SmogRank / Episodes / United States

Western United States, September 2023

For 6 days, from 19 to 24 September 2023, 61 cities in the United States and Mexico had PM2.5 at least twice their usual for the time of year. The worst reading was San Jose, California, United States: 47.7 µg/m³ on 20 September, about 6.1× its usual 7.8.

No cause namedWe have no fire or smoke records for these days, so we only say what the measurements show.
Cities reached61in 2 countries
Days619 to 24 September 2023
Worst day22 September50 cities counted
Furthest above usual8.8×Pleasanton

Day by day

22 September 50 cities at twice their usual or more
FillmoreSanta ClaritaLancasterSimi ValleyThousand OaksAgouraLa Crescenta-MontroseBurbankGlendoraLomitaVictorvilleRiversideLake ElsinoreBanningSouth Lake TahoeCarson CityTruckeePowayRenoIndioSan DiegoSpanish SpringsEl CajonChula VistaSummerlin SouthEnterpriseSpring ValleyLas VegasHendersonBoulder CityBrawleyEl CentroCalexicoYumaJurupa ValleyTijuanaLos AngelesFontanaBakersfieldVisaliaPortervilleAnaheimSanta MonicaHawthorneMexicaliHanfordOceansideComptonCarsonCorcoranInglewoodLong BeachTorranceSanta BarbaraFresnoClovisMaderaTurlockRichmondModestoArden-ArcadeYuba CityMercedWoodlandOrcuttUkiahStocktonRosevilleArroyo GrandeVacavilleDavisTracyMantecaAtascaderoNipomoLincolnSacramentoFolsomSan JoseSalinasLompocSan Luis ObispoGaltSan LeandroSan FranciscoSanta CruzHollisterSan RafaelRedwood CityOaklandLivermoreConcordSanta RosaGilroyPleasanton
16 Sep1718192021222324252627
Every measured city in the area, coloured by its PM2.5 that day; a dark ring marks a city at twice its usual or more. Bars: cities counted each day, coloured by their median level. Choose a day or press play; without JavaScript, the days link to that day's world ranking.

How it spread

MexicaliMexicali, 16 September: 42.9 µg/m³, 3.0× usualMexicali, 17 September: 33.5 µg/m³, 2.4× usualMexicali, 18 September: 35.7 µg/m³, 2.5× usualMexicali, 19 September: 34.6 µg/m³, 2.4× usualMexicali, 20 September: 33.6 µg/m³, 2.4× usualMexicali, 21 September: 40.1 µg/m³, 2.8× usualMexicali, 22 September: 39.2 µg/m³, 2.8× usualMexicali, 23 September: 35.3 µg/m³, 2.5× usualMexicali, 24 September: 36.2 µg/m³, 2.5× usualMexicali, 25 September: 34.2 µg/m³, 2.4× usualMexicali, 26 September: 34.5 µg/m³, 2.4× usualMexicali, 27 September: 26.7 µg/m³, 1.9× usualFontanaFontana, 16 September: 25.6 µg/m³, 2.2× usualFontana, 17 September: 16.5 µg/m³, 1.4× usualFontana, 18 September: 11.8 µg/m³, 1.0× usualFontana, 19 September: 13.3 µg/m³, 1.1× usualFontana, 20 September: 11.7 µg/m³, 1.0× usualFontana, 21 September: 16.6 µg/m³, 1.4× usualFontana, 22 September: 22.2 µg/m³, 1.9× usualFontana, 23 September: 28.9 µg/m³, 2.4× usualFontana, 24 September: 27.2 µg/m³, 2.3× usualFontana, 25 September: 28.5 µg/m³, 2.4× usualFontana, 26 September: 20.5 µg/m³, 1.7× usualFontana, 27 September: 18.9 µg/m³, 1.6× usualOaklandOakland, 16 September: 7.8 µg/m³, 1.2× usualOakland, 17 September: 5.9 µg/m³, 0.9× usualOakland, 18 September: 6.4 µg/m³, 1.0× usualOakland, 19 September: 29.9 µg/m³, 4.7× usualOakland, 20 September: 46.1 µg/m³, 7.2× usualOakland, 21 September: 33.1 µg/m³, 5.2× usualOakland, 22 September: 34.2 µg/m³, 5.3× usualOakland, 23 September: 24.0 µg/m³, 3.8× usualOakland, 24 September: 6.3 µg/m³, 1.0× usualOakland, 25 September: 3.2 µg/m³, 0.5× usualOakland, 26 September: 5.3 µg/m³, 0.8× usualOakland, 27 September: 6.5 µg/m³, 1.0× usualSan FranciscoSan Francisco, 16 September: 8.7 µg/m³, 1.4× usualSan Francisco, 17 September: 5.8 µg/m³, 0.9× usualSan Francisco, 18 September: 6.5 µg/m³, 1.0× usualSan Francisco, 19 September: 32.1 µg/m³, 5.0× usualSan Francisco, 20 September: 43.8 µg/m³, 6.8× usualSan Francisco, 21 September: 29.2 µg/m³, 4.6× usualSan Francisco, 22 September: 32.8 µg/m³, 5.1× usualSan Francisco, 23 September: 23.7 µg/m³, 3.7× usualSan Francisco, 24 September: 4.9 µg/m³, 0.8× usualSan Francisco, 25 September: 3.0 µg/m³, 0.5× usualSan Francisco, 26 September: no readingSan Francisco, 27 September: no readingSalinasSalinas, 16 September: 11.0 µg/m³, 1.5× usualSalinas, 17 September: 10.7 µg/m³, 1.5× usualSalinas, 18 September: 8.7 µg/m³, 1.2× usualSalinas, 19 September: 25.4 µg/m³, 3.6× usualSalinas, 20 September: 43.6 µg/m³, 6.1× usualSalinas, 21 September: 34.6 µg/m³, 4.9× usualSalinas, 22 September: 29.0 µg/m³, 4.1× usualSalinas, 23 September: 26.5 µg/m³, 3.7× usualSalinas, 24 September: 18.9 µg/m³, 2.7× usualSalinas, 25 September: 5.6 µg/m³, 0.8× usualSalinas, 26 September: 5.8 µg/m³, 0.8× usualSalinas, 27 September: 9.2 µg/m³, 1.3× usualSan LeandroSan Leandro, 16 September: 6.0 µg/m³, 1.0× usualSan Leandro, 17 September: 4.8 µg/m³, 0.8× usualSan Leandro, 18 September: 5.3 µg/m³, 0.8× usualSan Leandro, 19 September: 26.2 µg/m³, 4.2× usualSan Leandro, 20 September: 43.0 µg/m³, 6.8× usualSan Leandro, 21 September: 31.0 µg/m³, 4.9× usualSan Leandro, 22 September: 32.0 µg/m³, 5.1× usualSan Leandro, 23 September: 21.4 µg/m³, 3.4× usualSan Leandro, 24 September: 4.7 µg/m³, 0.7× usualSan Leandro, 25 September: 2.2 µg/m³, 0.3× usualSan Leandro, 26 September: 3.6 µg/m³, 0.6× usualSan Leandro, 27 September: 4.3 µg/m³, 0.7× usualRedwood CityRedwood City, 16 September: 8.9 µg/m³, 1.5× usualRedwood City, 17 September: 7.5 µg/m³, 1.3× usualRedwood City, 18 September: 6.5 µg/m³, 1.1× usualRedwood City, 19 September: 27.8 µg/m³, 4.6× usualRedwood City, 20 September: 42.3 µg/m³, 7.1× usualRedwood City, 21 September: 33.3 µg/m³, 5.6× usualRedwood City, 22 September: 31.1 µg/m³, 5.2× usualRedwood City, 23 September: 23.0 µg/m³, 3.8× usualRedwood City, 24 September: 11.4 µg/m³, 1.9× usualRedwood City, 25 September: 4.6 µg/m³, 0.8× usualRedwood City, 26 September: 5.6 µg/m³, 0.9× usualRedwood City, 27 September: 7.3 µg/m³, 1.2× usualRichmondRichmond, 16 September: 20.9 µg/m³, 2.2× usualRichmond, 17 September: 18.2 µg/m³, 1.9× usualRichmond, 18 September: 14.3 µg/m³, 1.5× usualRichmond, 19 September: 29.0 µg/m³, 3.0× usualRichmond, 20 September: 40.3 µg/m³, 4.2× usualRichmond, 21 September: 36.2 µg/m³, 3.8× usualRichmond, 22 September: 35.9 µg/m³, 3.7× usualRichmond, 23 September: 25.0 µg/m³, 2.6× usualRichmond, 24 September: 7.5 µg/m³, 0.8× usualRichmond, 25 September: 5.6 µg/m³, 0.6× usualRichmond, 26 September: no readingRichmond, 27 September: no readingSan RafaelSan Rafael, 16 September: 7.1 µg/m³, 1.4× usualSan Rafael, 17 September: 4.9 µg/m³, 1.0× usualSan Rafael, 18 September: 5.3 µg/m³, 1.1× usualSan Rafael, 19 September: 25.6 µg/m³, 5.1× usualSan Rafael, 20 September: 31.5 µg/m³, 6.3× usualSan Rafael, 21 September: 29.3 µg/m³, 5.9× usualSan Rafael, 22 September: 35.7 µg/m³, 7.1× usualSan Rafael, 23 September: 21.3 µg/m³, 4.3× usualSan Rafael, 24 September: 4.8 µg/m³, 1.0× usualSan Rafael, 25 September: 2.8 µg/m³, 0.6× usualSan Rafael, 26 September: 3.4 µg/m³, 0.7× usualSan Rafael, 27 September: 4.3 µg/m³, 0.9× usualSan JoseSan Jose, 16 September: 9.3 µg/m³, 1.2× usualSan Jose, 17 September: 6.7 µg/m³, 0.9× usualSan Jose, 18 September: 6.2 µg/m³, 0.8× usualSan Jose, 19 September: 22.7 µg/m³, 2.9× usualSan Jose, 20 September: 47.7 µg/m³, 6.1× usualSan Jose, 21 September: 33.1 µg/m³, 4.2× usualSan Jose, 22 September: 33.3 µg/m³, 4.3× usualSan Jose, 23 September: 23.9 µg/m³, 3.1× usualSan Jose, 24 September: 14.4 µg/m³, 1.8× usualSan Jose, 25 September: 4.4 µg/m³, 0.6× usualSan Jose, 26 September: 3.6 µg/m³, 0.5× usualSan Jose, 27 September: 5.3 µg/m³, 0.7× usualPleasantonPleasanton, 16 September: no readingPleasanton, 17 September: no readingPleasanton, 18 September: no readingPleasanton, 19 September: 24.1 µg/m³, 4.7× usualPleasanton, 20 September: 44.9 µg/m³, 8.8× usualPleasanton, 21 September: 34.0 µg/m³, 6.7× usualPleasanton, 22 September: 31.0 µg/m³, 6.1× usualPleasanton, 23 September: 25.2 µg/m³, 4.9× usualPleasanton, 24 September: 9.7 µg/m³, 1.9× usualPleasanton, 25 September: 3.2 µg/m³, 0.6× usualPleasanton, 26 September: 4.5 µg/m³, 0.9× usualPleasanton, 27 September: 4.5 µg/m³, 0.9× usualLivermoreLivermore, 16 September: 7.8 µg/m³, 1.4× usualLivermore, 17 September: 4.6 µg/m³, 0.8× usualLivermore, 18 September: 5.4 µg/m³, 0.9× usualLivermore, 19 September: 20.4 µg/m³, 3.6× usualLivermore, 20 September: 43.0 µg/m³, 7.5× usualLivermore, 21 September: 28.7 µg/m³, 5.0× usualLivermore, 22 September: 28.0 µg/m³, 4.9× usualLivermore, 23 September: 22.8 µg/m³, 4.0× usualLivermore, 24 September: 9.5 µg/m³, 1.7× usualLivermore, 25 September: 2.5 µg/m³, 0.4× usualLivermore, 26 September: 3.8 µg/m³, 0.7× usualLivermore, 27 September: 4.6 µg/m³, 0.8× usualGilroyGilroy, 16 September: 3.4 µg/m³, 0.7× usualGilroy, 17 September: 3.5 µg/m³, 0.7× usualGilroy, 18 September: 2.4 µg/m³, 0.5× usualGilroy, 19 September: 10.6 µg/m³, 2.1× usualGilroy, 20 September: 42.5 µg/m³, 8.5× usualGilroy, 21 September: 29.0 µg/m³, 5.8× usualGilroy, 22 September: 26.8 µg/m³, 5.4× usualGilroy, 23 September: 17.5 µg/m³, 3.5× usualGilroy, 24 September: 13.5 µg/m³, 2.7× usualGilroy, 25 September: 0.6 µg/m³, 0.1× usualGilroy, 26 September: 2.0 µg/m³, 0.4× usualGilroy, 27 September: 1.5 µg/m³, 0.3× usualSanta RosaSanta Rosa, 16 September: 3.9 µg/m³, 0.8× usualSanta Rosa, 17 September: 3.9 µg/m³, 0.8× usualSanta Rosa, 18 September: 4.5 µg/m³, 0.9× usualSanta Rosa, 19 September: 18.6 µg/m³, 3.7× usualSanta Rosa, 20 September: 41.4 µg/m³, 8.3× usualSanta Rosa, 21 September: 38.3 µg/m³, 7.7× usualSanta Rosa, 22 September: 33.4 µg/m³, 6.7× usualSanta Rosa, 23 September: 17.9 µg/m³, 3.6× usualSanta Rosa, 24 September: 6.2 µg/m³, 1.2× usualSanta Rosa, 25 September: 1.4 µg/m³, 0.3× usualSanta Rosa, 26 September: 1.8 µg/m³, 0.4× usualSanta Rosa, 27 September: 1.6 µg/m³, 0.3× usualHollisterHollister, 16 September: 6.8 µg/m³, 1.2× usualHollister, 17 September: 6.1 µg/m³, 1.1× usualHollister, 18 September: 3.8 µg/m³, 0.7× usualHollister, 19 September: 12.9 µg/m³, 2.2× usualHollister, 20 September: 41.3 µg/m³, 7.1× usualHollister, 21 September: 31.6 µg/m³, 5.4× usualHollister, 22 September: 27.0 µg/m³, 4.7× usualHollister, 23 September: 18.9 µg/m³, 3.3× usualHollister, 24 September: 14.1 µg/m³, 2.4× usualHollister, 25 September: 3.1 µg/m³, 0.5× usualHollister, 26 September: 2.6 µg/m³, 0.4× usualHollister, 27 September: 4.4 µg/m³, 0.8× usualSanta CruzSanta Cruz, 16 September: 5.2 µg/m³, 0.9× usualSanta Cruz, 17 September: 5.5 µg/m³, 0.9× usualSanta Cruz, 18 September: 4.3 µg/m³, 0.7× usualSanta Cruz, 19 September: 13.0 µg/m³, 2.2× usualSanta Cruz, 20 September: 40.1 µg/m³, 6.9× usualSanta Cruz, 21 September: 31.7 µg/m³, 5.5× usualSanta Cruz, 22 September: 27.3 µg/m³, 4.7× usualSanta Cruz, 23 September: 19.7 µg/m³, 3.4× usualSanta Cruz, 24 September: 11.6 µg/m³, 2.0× usualSanta Cruz, 25 September: 2.8 µg/m³, 0.5× usualSanta Cruz, 26 September: 3.4 µg/m³, 0.6× usualSanta Cruz, 27 September: 3.0 µg/m³, 0.5× usualConcordConcord, 16 September: 6.5 µg/m³, 1.3× usualConcord, 17 September: 4.0 µg/m³, 0.8× usualConcord, 18 September: 3.3 µg/m³, 0.7× usualConcord, 19 September: 18.1 µg/m³, 3.6× usualConcord, 20 September: 39.3 µg/m³, 7.9× usualConcord, 21 September: 29.5 µg/m³, 5.9× usualConcord, 22 September: 29.9 µg/m³, 6.0× usualConcord, 23 September: 20.8 µg/m³, 4.2× usualConcord, 24 September: 5.3 µg/m³, 1.1× usualConcord, 25 September: 2.4 µg/m³, 0.5× usualConcord, 26 September: 2.1 µg/m³, 0.4× usualConcord, 27 September: 2.7 µg/m³, 0.5× usualMantecaManteca, 16 September: 9.0 µg/m³, 1.3× usualManteca, 17 September: 6.6 µg/m³, 1.0× usualManteca, 18 September: 4.2 µg/m³, 0.6× usualManteca, 19 September: 12.2 µg/m³, 1.8× usualManteca, 20 September: 37.9 µg/m³, 5.5× usualManteca, 21 September: 26.7 µg/m³, 3.9× usualManteca, 22 September: 33.4 µg/m³, 4.8× usualManteca, 23 September: 24.8 µg/m³, 3.6× usualManteca, 24 September: 15.5 µg/m³, 2.2× usualManteca, 25 September: 4.3 µg/m³, 0.6× usualManteca, 26 September: 4.3 µg/m³, 0.6× usualManteca, 27 September: 4.4 µg/m³, 0.6× usualStocktonStockton, 16 September: 10.3 µg/m³, 1.5× usualStockton, 17 September: 7.8 µg/m³, 1.1× usualStockton, 18 September: 6.3 µg/m³, 0.9× usualStockton, 19 September: 12.3 µg/m³, 1.7× usualStockton, 20 September: 37.1 µg/m³, 5.2× usualStockton, 21 September: 26.0 µg/m³, 3.7× usualStockton, 22 September: 33.7 µg/m³, 4.7× usualStockton, 23 September: 23.9 µg/m³, 3.4× usualStockton, 24 September: 15.1 µg/m³, 2.1× usualStockton, 25 September: 5.4 µg/m³, 0.8× usualStockton, 26 September: 5.9 µg/m³, 0.8× usualStockton, 27 September: 5.9 µg/m³, 0.8× usualGaltGalt, 16 September: 8.9 µg/m³, 1.6× usualGalt, 17 September: 6.0 µg/m³, 1.1× usualGalt, 18 September: 4.4 µg/m³, 0.8× usualGalt, 19 September: 13.7 µg/m³, 2.4× usualGalt, 20 September: 36.8 µg/m³, 6.6× usualGalt, 21 September: 26.0 µg/m³, 4.6× usualGalt, 22 September: 30.5 µg/m³, 5.4× usualGalt, 23 September: 21.7 µg/m³, 3.9× usualGalt, 24 September: 8.8 µg/m³, 1.6× usualGalt, 25 September: 2.6 µg/m³, 0.5× usualGalt, 26 September: 3.4 µg/m³, 0.6× usualGalt, 27 September: 4.1 µg/m³, 0.7× usualSacramentoSacramento, 16 September: 5.4 µg/m³, 0.9× usualSacramento, 17 September: 5.1 µg/m³, 0.9× usualSacramento, 18 September: 5.1 µg/m³, 0.9× usualSacramento, 19 September: 13.1 µg/m³, 2.2× usualSacramento, 20 September: 34.7 µg/m³, 5.8× usualSacramento, 21 September: 25.4 µg/m³, 4.2× usualSacramento, 22 September: 30.3 µg/m³, 5.1× usualSacramento, 23 September: 20.2 µg/m³, 3.4× usualSacramento, 24 September: 7.8 µg/m³, 1.3× usualSacramento, 25 September: 2.3 µg/m³, 0.4× usualSacramento, 26 September: 3.2 µg/m³, 0.5× usualSacramento, 27 September: 3.7 µg/m³, 0.6× usualSan Luis ObispoSan Luis Obispo, 16 September: 8.7 µg/m³, 1.6× usualSan Luis Obispo, 17 September: 6.8 µg/m³, 1.3× usualSan Luis Obispo, 18 September: 4.8 µg/m³, 0.9× usualSan Luis Obispo, 19 September: 7.9 µg/m³, 1.5× usualSan Luis Obispo, 20 September: 34.5 µg/m³, 6.4× usualSan Luis Obispo, 21 September: 29.3 µg/m³, 5.4× usualSan Luis Obispo, 22 September: 28.7 µg/m³, 5.3× usualSan Luis Obispo, 23 September: 24.2 µg/m³, 4.5× usualSan Luis Obispo, 24 September: 18.2 µg/m³, 3.4× usualSan Luis Obispo, 25 September: 6.2 µg/m³, 1.1× usualSan Luis Obispo, 26 September: 4.5 µg/m³, 0.8× usualSan Luis Obispo, 27 September: 5.8 µg/m³, 1.1× usualNipomoNipomo, 16 September: 9.9 µg/m³, 1.7× usualNipomo, 17 September: 7.0 µg/m³, 1.2× usualNipomo, 18 September: 4.9 µg/m³, 0.8× usualNipomo, 19 September: 9.7 µg/m³, 1.6× usualNipomo, 20 September: 34.1 µg/m³, 5.7× usualNipomo, 21 September: 31.8 µg/m³, 5.3× usualNipomo, 22 September: 29.0 µg/m³, 4.8× usualNipomo, 23 September: 24.6 µg/m³, 4.1× usualNipomo, 24 September: 19.6 µg/m³, 3.3× usualNipomo, 25 September: 8.0 µg/m³, 1.3× usualNipomo, 26 September: 12.5 µg/m³, 2.1× usualNipomo, 27 September: 18.7 µg/m³, 3.1× usualArroyo GrandeArroyo Grande, 16 September: 10.3 µg/m³, 1.6× usualArroyo Grande, 17 September: 8.7 µg/m³, 1.4× usualArroyo Grande, 18 September: 5.5 µg/m³, 0.9× usualArroyo Grande, 19 September: 12.8 µg/m³, 2.0× usualArroyo Grande, 20 September: 33.7 µg/m³, 5.3× usualArroyo Grande, 21 September: 32.1 µg/m³, 5.1× usualArroyo Grande, 22 September: 30.7 µg/m³, 4.9× usualArroyo Grande, 23 September: 24.7 µg/m³, 3.9× usualArroyo Grande, 24 September: 19.5 µg/m³, 3.1× usualArroyo Grande, 25 September: 8.6 µg/m³, 1.4× usualArroyo Grande, 26 September: 12.5 µg/m³, 2.0× usualArroyo Grande, 27 September: 16.4 µg/m³, 2.6× usualWoodlandWoodland, 16 September: 7.2 µg/m³, 1.1× usualWoodland, 17 September: 6.2 µg/m³, 0.9× usualWoodland, 18 September: 6.4 µg/m³, 0.9× usualWoodland, 19 September: 13.8 µg/m³, 2.0× usualWoodland, 20 September: 33.5 µg/m³, 4.9× usualWoodland, 21 September: 26.9 µg/m³, 4.0× usualWoodland, 22 September: 32.8 µg/m³, 4.8× usualWoodland, 23 September: 21.8 µg/m³, 3.2× usualWoodland, 24 September: 8.9 µg/m³, 1.3× usualWoodland, 25 September: 3.3 µg/m³, 0.5× usualWoodland, 26 September: 2.5 µg/m³, 0.4× usualWoodland, 27 September: 5.1 µg/m³, 0.8× usualLincolnLincoln, 16 September: 9.3 µg/m³, 1.6× usualLincoln, 17 September: 8.7 µg/m³, 1.5× usualLincoln, 18 September: 7.3 µg/m³, 1.3× usualLincoln, 19 September: 9.3 µg/m³, 1.6× usualLincoln, 20 September: 32.4 µg/m³, 5.7× usualLincoln, 21 September: 25.2 µg/m³, 4.4× usualLincoln, 22 September: 27.3 µg/m³, 4.8× usualLincoln, 23 September: 20.2 µg/m³, 3.5× usualLincoln, 24 September: 13.4 µg/m³, 2.4× usualLincoln, 25 September: 3.3 µg/m³, 0.6× usualLincoln, 26 September: no readingLincoln, 27 September: no readingLompocLompoc, 16 September: no readingLompoc, 17 September: no readingLompoc, 18 September: no readingLompoc, 19 September: 8.2 µg/m³, 1.6× usualLompoc, 20 September: 30.0 µg/m³, 5.8× usualLompoc, 21 September: 32.3 µg/m³, 6.2× usualLompoc, 22 September: 29.0 µg/m³, 5.6× usualLompoc, 23 September: 25.8 µg/m³, 5.0× usualLompoc, 24 September: 18.7 µg/m³, 3.6× usualLompoc, 25 September: 8.9 µg/m³, 1.7× usualLompoc, 26 September: 4.7 µg/m³, 0.9× usualLompoc, 27 September: 9.2 µg/m³, 1.8× usualArden-ArcadeArden-Arcade, 16 September: 4.3 µg/m³, 0.6× usualArden-Arcade, 17 September: 3.2 µg/m³, 0.5× usualArden-Arcade, 18 September: 2.9 µg/m³, 0.4× usualArden-Arcade, 19 September: 10.2 µg/m³, 1.4× usualArden-Arcade, 20 September: 32.2 µg/m³, 4.5× usualArden-Arcade, 21 September: 23.3 µg/m³, 3.3× usualArden-Arcade, 22 September: 27.7 µg/m³, 3.9× usualArden-Arcade, 23 September: 18.6 µg/m³, 2.6× usualArden-Arcade, 24 September: 8.1 µg/m³, 1.1× usualArden-Arcade, 25 September: 1.2 µg/m³, 0.2× usualArden-Arcade, 26 September: 0.5 µg/m³, 0.1× usualArden-Arcade, 27 September: 2.3 µg/m³, 0.3× usualModestoModesto, 16 September: 10.8 µg/m³, 1.5× usualModesto, 17 September: 7.8 µg/m³, 1.1× usualModesto, 18 September: 7.4 µg/m³, 1.0× usualModesto, 19 September: 10.9 µg/m³, 1.5× usualModesto, 20 September: 31.3 µg/m³, 4.3× usualModesto, 21 September: 25.8 µg/m³, 3.5× usualModesto, 22 September: 32.2 µg/m³, 4.4× usualModesto, 23 September: 24.7 µg/m³, 3.4× usualModesto, 24 September: 18.3 µg/m³, 2.5× usualModesto, 25 September: 6.0 µg/m³, 0.8× usualModesto, 26 September: 4.7 µg/m³, 0.6× usualModesto, 27 September: 6.2 µg/m³, 0.8× usualFolsomFolsom, 16 September: 7.5 µg/m³, 1.4× usualFolsom, 17 September: 6.8 µg/m³, 1.3× usualFolsom, 18 September: 5.1 µg/m³, 0.9× usualFolsom, 19 September: 9.7 µg/m³, 1.8× usualFolsom, 20 September: 31.8 µg/m³, 5.9× usualFolsom, 21 September: 25.9 µg/m³, 4.8× usualFolsom, 22 September: 27.3 µg/m³, 5.1× usualFolsom, 23 September: 21.4 µg/m³, 4.0× usualFolsom, 24 September: 13.2 µg/m³, 2.4× usualFolsom, 25 September: 5.4 µg/m³, 1.0× usualFolsom, 26 September: 9.4 µg/m³, 1.7× usualFolsom, 27 September: 5.0 µg/m³, 0.9× usualRosevilleRoseville, 16 September: 8.6 µg/m³, 1.4× usualRoseville, 17 September: 6.9 µg/m³, 1.2× usualRoseville, 18 September: 7.2 µg/m³, 1.2× usualRoseville, 19 September: 10.6 µg/m³, 1.8× usualRoseville, 20 September: 31.8 µg/m³, 5.3× usualRoseville, 21 September: 24.8 µg/m³, 4.1× usualRoseville, 22 September: 26.6 µg/m³, 4.4× usualRoseville, 23 September: 20.5 µg/m³, 3.4× usualRoseville, 24 September: 13.0 µg/m³, 2.2× usualRoseville, 25 September: 3.7 µg/m³, 0.6× usualRoseville, 26 September: 2.6 µg/m³, 0.4× usualRoseville, 27 September: 4.5 µg/m³, 0.8× usualTurlockTurlock, 16 September: 11.2 µg/m³, 1.4× usualTurlock, 17 September: 9.0 µg/m³, 1.1× usualTurlock, 18 September: 6.9 µg/m³, 0.9× usualTurlock, 19 September: 11.0 µg/m³, 1.4× usualTurlock, 20 September: 28.8 µg/m³, 3.6× usualTurlock, 21 September: 28.4 µg/m³, 3.6× usualTurlock, 22 September: 31.1 µg/m³, 3.9× usualTurlock, 23 September: 26.8 µg/m³, 3.4× usualTurlock, 24 September: 19.6 µg/m³, 2.5× usualTurlock, 25 September: 6.7 µg/m³, 0.8× usualTurlock, 26 September: 6.8 µg/m³, 0.9× usualTurlock, 27 September: 7.1 µg/m³, 0.9× usualYuba CityYuba City, 16 September: 9.8 µg/m³, 1.5× usualYuba City, 17 September: 8.5 µg/m³, 1.3× usualYuba City, 18 September: 8.5 µg/m³, 1.3× usualYuba City, 19 September: 8.9 µg/m³, 1.3× usualYuba City, 20 September: 30.4 µg/m³, 4.5× usualYuba City, 21 September: 19.1 µg/m³, 2.9× usualYuba City, 22 September: 26.9 µg/m³, 4.0× usualYuba City, 23 September: 21.8 µg/m³, 3.3× usualYuba City, 24 September: 15.3 µg/m³, 2.3× usualYuba City, 25 September: 3.9 µg/m³, 0.6× usualYuba City, 26 September: 3.7 µg/m³, 0.6× usualYuba City, 27 September: 6.5 µg/m³, 1.0× usualUkiahUkiah, 16 September: 5.5 µg/m³, 0.9× usualUkiah, 17 September: 4.5 µg/m³, 0.8× usualUkiah, 18 September: 5.9 µg/m³, 1.0× usualUkiah, 19 September: 10.5 µg/m³, 1.8× usualUkiah, 20 September: 25.1 µg/m³, 4.3× usualUkiah, 21 September: 27.4 µg/m³, 4.7× usualUkiah, 22 September: 29.8 µg/m³, 5.1× usualUkiah, 23 September: no readingUkiah, 24 September: no readingUkiah, 25 September: no readingUkiah, 26 September: no readingUkiah, 27 September: 7.9 µg/m³, 1.4× usualDavisDavis, 16 September: 8.4 µg/m³, 1.6× usualDavis, 17 September: 7.1 µg/m³, 1.3× usualDavis, 18 September: 6.4 µg/m³, 1.2× usualDavis, 19 September: 15.3 µg/m³, 2.8× usualDavis, 20 September: 28.7 µg/m³, 5.3× usualDavis, 21 September: 27.4 µg/m³, 5.1× usualDavis, 22 September: 29.1 µg/m³, 5.4× usualDavis, 23 September: 21.9 µg/m³, 4.1× usualDavis, 24 September: 8.2 µg/m³, 1.5× usualDavis, 25 September: 2.9 µg/m³, 0.5× usualDavis, 26 September: 2.6 µg/m³, 0.5× usualDavis, 27 September: 4.1 µg/m³, 0.8× usualVacavilleVacaville, 16 September: 3.8 µg/m³, 0.8× usualVacaville, 17 September: 3.1 µg/m³, 0.6× usualVacaville, 18 September: 3.7 µg/m³, 0.7× usualVacaville, 19 September: 13.2 µg/m³, 2.6× usualVacaville, 20 September: 26.3 µg/m³, 5.3× usualVacaville, 21 September: 21.7 µg/m³, 4.3× usualVacaville, 22 September: 26.8 µg/m³, 5.4× usualVacaville, 23 September: 16.9 µg/m³, 3.4× usualVacaville, 24 September: 6.1 µg/m³, 1.2× usualVacaville, 25 September: 2.5 µg/m³, 0.5× usualVacaville, 26 September: 2.5 µg/m³, 0.5× usualVacaville, 27 September: 2.1 µg/m³, 0.4× usualOrcuttOrcutt, 16 September: 5.5 µg/m³, 1.0× usualOrcutt, 17 September: 4.9 µg/m³, 0.9× usualOrcutt, 18 September: 3.4 µg/m³, 0.6× usualOrcutt, 19 September: 6.7 µg/m³, 1.2× usualOrcutt, 20 September: 26.7 µg/m³, 4.9× usualOrcutt, 21 September: 25.0 µg/m³, 4.6× usualOrcutt, 22 September: 25.0 µg/m³, 4.6× usualOrcutt, 23 September: 21.7 µg/m³, 4.0× usualOrcutt, 24 September: 17.3 µg/m³, 3.2× usualOrcutt, 25 September: 6.4 µg/m³, 1.2× usualOrcutt, 26 September: 4.5 µg/m³, 0.8× usualOrcutt, 27 September: 5.9 µg/m³, 1.1× usualMaderaMadera, 16 September: 13.7 µg/m³, 1.5× usualMadera, 17 September: 11.9 µg/m³, 1.3× usualMadera, 18 September: 9.0 µg/m³, 1.0× usualMadera, 19 September: 8.7 µg/m³, 0.9× usualMadera, 20 September: 18.9 µg/m³, 2.0× usualMadera, 21 September: 35.0 µg/m³, 3.8× usualMadera, 22 September: 27.8 µg/m³, 3.0× usualMadera, 23 September: 27.5 µg/m³, 3.0× usualMadera, 24 September: 21.4 µg/m³, 2.3× usualMadera, 25 September: 8.5 µg/m³, 0.9× usualMadera, 26 September: 6.5 µg/m³, 0.7× usualMadera, 27 September: 7.4 µg/m³, 0.8× usualFresnoFresno, 16 September: 11.5 µg/m³, 1.1× usualFresno, 17 September: 10.0 µg/m³, 1.0× usualFresno, 18 September: 8.2 µg/m³, 0.8× usualFresno, 19 September: 8.3 µg/m³, 0.8× usualFresno, 20 September: 15.9 µg/m³, 1.5× usualFresno, 21 September: 34.0 µg/m³, 3.2× usualFresno, 22 September: 28.0 µg/m³, 2.7× usualFresno, 23 September: 25.7 µg/m³, 2.4× usualFresno, 24 September: 22.3 µg/m³, 2.1× usualFresno, 25 September: 11.8 µg/m³, 1.1× usualFresno, 26 September: 5.6 µg/m³, 0.5× usualFresno, 27 September: 7.2 µg/m³, 0.7× usualClovisClovis, 16 September: 11.1 µg/m³, 1.2× usualClovis, 17 September: 8.2 µg/m³, 0.9× usualClovis, 18 September: 6.1 µg/m³, 0.6× usualClovis, 19 September: 7.4 µg/m³, 0.8× usualClovis, 20 September: 13.5 µg/m³, 1.4× usualClovis, 21 September: 33.6 µg/m³, 3.5× usualClovis, 22 September: 24.7 µg/m³, 2.6× usualClovis, 23 September: 23.6 µg/m³, 2.5× usualClovis, 24 September: 22.3 µg/m³, 2.3× usualClovis, 25 September: 9.1 µg/m³, 1.0× usualClovis, 26 September: 3.6 µg/m³, 0.4× usualClovis, 27 September: 5.2 µg/m³, 0.5× usualMercedMerced, 16 September: 8.9 µg/m³, 1.3× usualMerced, 17 September: 7.0 µg/m³, 1.0× usualMerced, 18 September: 5.1 µg/m³, 0.7× usualMerced, 19 September: 6.1 µg/m³, 0.9× usualMerced, 20 September: 18.6 µg/m³, 2.7× usualMerced, 21 September: 32.7 µg/m³, 4.7× usualMerced, 22 September: 25.8 µg/m³, 3.7× usualMerced, 23 September: 24.5 µg/m³, 3.6× usualMerced, 24 September: 17.0 µg/m³, 2.5× usualMerced, 25 September: 4.6 µg/m³, 0.7× usualMerced, 26 September: 2.9 µg/m³, 0.4× usualMerced, 27 September: 4.9 µg/m³, 0.7× usualHanfordHanford, 16 September: 11.5 µg/m³, 1.1× usualHanford, 17 September: 8.9 µg/m³, 0.8× usualHanford, 18 September: 9.3 µg/m³, 0.9× usualHanford, 19 September: 9.0 µg/m³, 0.8× usualHanford, 20 September: 18.2 µg/m³, 1.7× usualHanford, 21 September: 30.4 µg/m³, 2.8× usualHanford, 22 September: 29.0 µg/m³, 2.7× usualHanford, 23 September: 26.5 µg/m³, 2.5× usualHanford, 24 September: 23.5 µg/m³, 2.2× usualHanford, 25 September: 10.1 µg/m³, 0.9× usualHanford, 26 September: 6.1 µg/m³, 0.6× usualHanford, 27 September: 6.2 µg/m³, 0.6× usualAtascaderoAtascadero, 16 September: 7.1 µg/m³, 1.4× usualAtascadero, 17 September: 5.1 µg/m³, 1.0× usualAtascadero, 18 September: 3.5 µg/m³, 0.7× usualAtascadero, 19 September: 6.8 µg/m³, 1.4× usualAtascadero, 20 September: 23.3 µg/m³, 4.7× usualAtascadero, 21 September: 28.7 µg/m³, 5.7× usualAtascadero, 22 September: 24.0 µg/m³, 4.8× usualAtascadero, 23 September: 19.3 µg/m³, 3.9× usualAtascadero, 24 September: 14.8 µg/m³, 3.0× usualAtascadero, 25 September: 7.4 µg/m³, 1.5× usualAtascadero, 26 September: 2.5 µg/m³, 0.5× usualAtascadero, 27 September: 3.4 µg/m³, 0.7× usualCorcoranCorcoran, 16 September: 11.7 µg/m³, 1.2× usualCorcoran, 17 September: 8.9 µg/m³, 0.9× usualCorcoran, 18 September: 6.5 µg/m³, 0.7× usualCorcoran, 19 September: 8.3 µg/m³, 0.9× usualCorcoran, 20 September: 14.2 µg/m³, 1.5× usualCorcoran, 21 September: 25.2 µg/m³, 2.6× usualCorcoran, 22 September: 27.8 µg/m³, 2.9× usualCorcoran, 23 September: 25.1 µg/m³, 2.6× usualCorcoran, 24 September: 21.7 µg/m³, 2.2× usualCorcoran, 25 September: 10.8 µg/m³, 1.1× usualCorcoran, 26 September: 4.8 µg/m³, 0.5× usualCorcoran, 27 September: 6.2 µg/m³, 0.6× usualVisaliaVisalia, 16 September: 13.6 µg/m³, 1.3× usualVisalia, 17 September: 9.4 µg/m³, 0.9× usualVisalia, 18 September: 7.3 µg/m³, 0.7× usualVisalia, 19 September: 9.6 µg/m³, 0.9× usualVisalia, 20 September: 13.0 µg/m³, 1.2× usualVisalia, 21 September: 25.4 µg/m³, 2.4× usualVisalia, 22 September: 26.6 µg/m³, 2.5× usualVisalia, 23 September: 25.8 µg/m³, 2.4× usualVisalia, 24 September: 24.4 µg/m³, 2.3× usualVisalia, 25 September: 14.8 µg/m³, 1.4× usualVisalia, 26 September: 6.5 µg/m³, 0.6× usualVisalia, 27 September: 7.6 µg/m³, 0.7× usualComptonCompton, 16 September: 10.4 µg/m³, 1.1× usualCompton, 17 September: 6.5 µg/m³, 0.7× usualCompton, 18 September: 10.1 µg/m³, 1.0× usualCompton, 19 September: 9.8 µg/m³, 1.0× usualCompton, 20 September: 12.7 µg/m³, 1.3× usualCompton, 21 September: 21.2 µg/m³, 2.2× usualCompton, 22 September: 28.0 µg/m³, 2.9× usualCompton, 23 September: 25.8 µg/m³, 2.6× usualCompton, 24 September: 26.8 µg/m³, 2.7× usualCompton, 25 September: 21.3 µg/m³, 2.2× usualCompton, 26 September: 12.3 µg/m³, 1.3× usualCompton, 27 September: 13.6 µg/m³, 1.4× usualTracyTracy, 16 September: no readingTracy, 17 September: no readingTracy, 18 September: no readingTracy, 19 September: no readingTracy, 20 September: no readingTracy, 21 September: 18.7 µg/m³, 3.7× usualTracy, 22 September: 27.4 µg/m³, 5.5× usualTracy, 23 September: 22.9 µg/m³, 4.6× usualTracy, 24 September: 12.6 µg/m³, 2.5× usualTracy, 25 September: 2.0 µg/m³, 0.4× usualTracy, 26 September: 2.8 µg/m³, 0.6× usualTracy, 27 September: 2.6 µg/m³, 0.5× usualBakersfieldBakersfield, 16 September: 12.7 µg/m³, 1.2× usualBakersfield, 17 September: 9.9 µg/m³, 0.9× usualBakersfield, 18 September: 6.8 µg/m³, 0.6× usualBakersfield, 19 September: 11.4 µg/m³, 1.0× usualBakersfield, 20 September: 14.4 µg/m³, 1.3× usualBakersfield, 21 September: 21.0 µg/m³, 1.9× usualBakersfield, 22 September: 27.4 µg/m³, 2.5× usualBakersfield, 23 September: 24.3 µg/m³, 2.2× usualBakersfield, 24 September: 21.3 µg/m³, 2.0× usualBakersfield, 25 September: 16.6 µg/m³, 1.5× usualBakersfield, 26 September: 10.9 µg/m³, 1.0× usualBakersfield, 27 September: 11.7 µg/m³, 1.1× usualLong BeachLong Beach, 16 September: 10.7 µg/m³, 1.2× usualLong Beach, 17 September: 11.8 µg/m³, 1.3× usualLong Beach, 18 September: 12.5 µg/m³, 1.4× usualLong Beach, 19 September: 8.4 µg/m³, 1.0× usualLong Beach, 20 September: 10.3 µg/m³, 1.2× usualLong Beach, 21 September: 17.9 µg/m³, 2.0× usualLong Beach, 22 September: 27.3 µg/m³, 3.1× usualLong Beach, 23 September: 23.2 µg/m³, 2.6× usualLong Beach, 24 September: 22.9 µg/m³, 2.6× usualLong Beach, 25 September: 19.4 µg/m³, 2.2× usualLong Beach, 26 September: 10.9 µg/m³, 1.2× usualLong Beach, 27 September: 9.9 µg/m³, 1.1× usualTorranceTorrance, 16 September: 8.5 µg/m³, 1.0× usualTorrance, 17 September: 6.8 µg/m³, 0.8× usualTorrance, 18 September: 7.9 µg/m³, 0.9× usualTorrance, 19 September: 8.7 µg/m³, 1.0× usualTorrance, 20 September: 11.9 µg/m³, 1.4× usualTorrance, 21 September: 19.4 µg/m³, 2.3× usualTorrance, 22 September: 25.9 µg/m³, 3.0× usualTorrance, 23 September: 25.4 µg/m³, 3.0× usualTorrance, 24 September: 26.9 µg/m³, 3.2× usualTorrance, 25 September: 22.2 µg/m³, 2.6× usualTorrance, 26 September: 10.8 µg/m³, 1.3× usualTorrance, 27 September: 8.7 µg/m³, 1.0× usualPortervillePorterville, 16 September: 14.1 µg/m³, 1.4× usualPorterville, 17 September: 10.5 µg/m³, 1.0× usualPorterville, 18 September: 8.4 µg/m³, 0.8× usualPorterville, 19 September: 12.0 µg/m³, 1.2× usualPorterville, 20 September: 13.3 µg/m³, 1.3× usualPorterville, 21 September: 24.5 µg/m³, 2.4× usualPorterville, 22 September: 26.7 µg/m³, 2.6× usualPorterville, 23 September: 23.6 µg/m³, 2.3× usualPorterville, 24 September: 20.2 µg/m³, 2.0× usualPorterville, 25 September: 18.0 µg/m³, 1.8× usualPorterville, 26 September: 9.9 µg/m³, 1.0× usualPorterville, 27 September: 10.0 µg/m³, 1.0× usualCarsonCarson, 16 September: 8.4 µg/m³, 0.9× usualCarson, 17 September: 6.7 µg/m³, 0.7× usualCarson, 18 September: 8.0 µg/m³, 0.9× usualCarson, 19 September: 9.0 µg/m³, 1.0× usualCarson, 20 September: 11.4 µg/m³, 1.2× usualCarson, 21 September: 19.7 µg/m³, 2.1× usualCarson, 22 September: 25.8 µg/m³, 2.8× usualCarson, 23 September: 25.3 µg/m³, 2.8× usualCarson, 24 September: 26.7 µg/m³, 2.9× usualCarson, 25 September: 21.4 µg/m³, 2.3× usualCarson, 26 September: 10.9 µg/m³, 1.2× usualCarson, 27 September: 9.4 µg/m³, 1.0× usualSanta BarbaraSanta Barbara, 16 September: 9.0 µg/m³, 1.1× usualSanta Barbara, 17 September: 7.6 µg/m³, 0.9× usualSanta Barbara, 18 September: 7.5 µg/m³, 0.9× usualSanta Barbara, 19 September: 6.5 µg/m³, 0.8× usualSanta Barbara, 20 September: 15.3 µg/m³, 1.9× usualSanta Barbara, 21 September: 22.5 µg/m³, 2.8× usualSanta Barbara, 22 September: 26.3 µg/m³, 3.2× usualSanta Barbara, 23 September: 24.5 µg/m³, 3.0× usualSanta Barbara, 24 September: 21.3 µg/m³, 2.6× usualSanta Barbara, 25 September: 14.3 µg/m³, 1.8× usualSanta Barbara, 26 September: 8.5 µg/m³, 1.0× usualSanta Barbara, 27 September: 8.0 µg/m³, 1.0× usualTijuanaTijuana, 16 September: 8.5 µg/m³, 0.6× usualTijuana, 17 September: 8.5 µg/m³, 0.6× usualTijuana, 18 September: 6.9 µg/m³, 0.5× usualTijuana, 19 September: 14.2 µg/m³, 1.0× usualTijuana, 20 September: 12.3 µg/m³, 0.9× usualTijuana, 21 September: 22.5 µg/m³, 1.6× usualTijuana, 22 September: 22.2 µg/m³, 1.6× usualTijuana, 23 September: 28.7 µg/m³, 2.1× usualTijuana, 24 September: 26.7 µg/m³, 1.9× usualTijuana, 25 September: 23.9 µg/m³, 1.7× usualTijuana, 26 September: 20.6 µg/m³, 1.5× usualTijuana, 27 September: 29.3 µg/m³, 2.1× usualAnaheimAnaheim, 16 September: 12.6 µg/m³, 1.3× usualAnaheim, 17 September: 6.0 µg/m³, 0.6× usualAnaheim, 18 September: 8.2 µg/m³, 0.8× usualAnaheim, 19 September: 9.0 µg/m³, 0.9× usualAnaheim, 20 September: 11.3 µg/m³, 1.2× usualAnaheim, 21 September: 18.8 µg/m³, 1.9× usualAnaheim, 22 September: 23.8 µg/m³, 2.5× usualAnaheim, 23 September: 26.5 µg/m³, 2.7× usualAnaheim, 24 September: 26.0 µg/m³, 2.7× usualAnaheim, 25 September: 23.3 µg/m³, 2.4× usualAnaheim, 26 September: 15.9 µg/m³, 1.6× usualAnaheim, 27 September: 13.4 µg/m³, 1.4× usualOceansideOceanside, 16 September: 6.1 µg/m³, 0.7× usualOceanside, 17 September: 5.9 µg/m³, 0.7× usualOceanside, 18 September: 7.1 µg/m³, 0.8× usualOceanside, 19 September: 7.2 µg/m³, 0.8× usualOceanside, 20 September: 10.4 µg/m³, 1.2× usualOceanside, 21 September: 16.7 µg/m³, 1.9× usualOceanside, 22 September: 18.5 µg/m³, 2.1× usualOceanside, 23 September: 26.4 µg/m³, 2.9× usualOceanside, 24 September: 23.9 µg/m³, 2.7× usualOceanside, 25 September: 21.1 µg/m³, 2.3× usualOceanside, 26 September: 13.0 µg/m³, 1.4× usualOceanside, 27 September: 11.3 µg/m³, 1.3× usualHawthorneHawthorne, 16 September: 8.8 µg/m³, 0.9× usualHawthorne, 17 September: 6.9 µg/m³, 0.7× usualHawthorne, 18 September: 8.0 µg/m³, 0.8× usualHawthorne, 19 September: 10.0 µg/m³, 1.1× usualHawthorne, 20 September: 10.6 µg/m³, 1.1× usualHawthorne, 21 September: 18.9 µg/m³, 2.0× usualHawthorne, 22 September: 24.2 µg/m³, 2.5× usualHawthorne, 23 September: 23.5 µg/m³, 2.5× usualHawthorne, 24 September: 26.7 µg/m³, 2.8× usualHawthorne, 25 September: 20.0 µg/m³, 2.1× usualHawthorne, 26 September: 10.5 µg/m³, 1.1× usualHawthorne, 27 September: 10.3 µg/m³, 1.1× usualLos AngelesLos Angeles, 16 September: 9.9 µg/m³, 0.9× usualLos Angeles, 17 September: 5.8 µg/m³, 0.5× usualLos Angeles, 18 September: 7.3 µg/m³, 0.6× usualLos Angeles, 19 September: 11.3 µg/m³, 1.0× usualLos Angeles, 20 September: 9.3 µg/m³, 0.8× usualLos Angeles, 21 September: 19.2 µg/m³, 1.7× usualLos Angeles, 22 September: 21.9 µg/m³, 1.9× usualLos Angeles, 23 September: 24.6 µg/m³, 2.2× usualLos Angeles, 24 September: 26.4 µg/m³, 2.3× usualLos Angeles, 25 September: 22.9 µg/m³, 2.0× usualLos Angeles, 26 September: 14.4 µg/m³, 1.3× usualLos Angeles, 27 September: 12.8 µg/m³, 1.1× usualInglewoodInglewood, 16 September: 8.7 µg/m³, 1.0× usualInglewood, 17 September: 6.7 µg/m³, 0.8× usualInglewood, 18 September: 7.6 µg/m³, 0.9× usualInglewood, 19 September: 9.7 µg/m³, 1.1× usualInglewood, 20 September: 11.0 µg/m³, 1.3× usualInglewood, 21 September: 18.1 µg/m³, 2.1× usualInglewood, 22 September: 21.0 µg/m³, 2.4× usualInglewood, 23 September: 24.0 µg/m³, 2.7× usualInglewood, 24 September: 26.3 µg/m³, 3.0× usualInglewood, 25 September: 20.2 µg/m³, 2.3× usualInglewood, 26 September: 11.9 µg/m³, 1.4× usualInglewood, 27 September: 9.0 µg/m³, 1.0× usualJurupa ValleyJurupa Valley, 16 September: 21.8 µg/m³, 1.8× usualJurupa Valley, 17 September: 9.2 µg/m³, 0.7× usualJurupa Valley, 18 September: 8.5 µg/m³, 0.7× usualJurupa Valley, 19 September: 10.5 µg/m³, 0.8× usualJurupa Valley, 20 September: 9.3 µg/m³, 0.8× usualJurupa Valley, 21 September: 14.0 µg/m³, 1.1× usualJurupa Valley, 22 September: 20.9 µg/m³, 1.7× usualJurupa Valley, 23 September: 24.5 µg/m³, 2.0× usualJurupa Valley, 24 September: 25.7 µg/m³, 2.1× usualJurupa Valley, 25 September: 25.1 µg/m³, 2.0× usualJurupa Valley, 26 September: 18.9 µg/m³, 1.5× usualJurupa Valley, 27 September: 15.4 µg/m³, 1.2× usual16 Sep1820222426
The 60 cities with the highest readings of 61, in the order the episode reached them, 3 days before to 3 after. Each square is a day, coloured by that day's PM2.5; outlined: at twice the city's usual or more.
Good0–50
Moderate51–100
Sensitive groups101–150
Unhealthy151–200
Very unhealthy201–300
Hazardous301+

Every city it reached

CityDaysHighestUsualAbove usual
PleasantonCalifornia, United States4 44.920 September5.18.8×
GilroyCalifornia, United States3 42.520 September4.68.5×
Santa RosaCalifornia, United States3 41.420 September2.98.3×
ConcordCalifornia, United States3 39.320 September4.17.9×
LivermoreCalifornia, United States3 43.020 September5.77.5×
OaklandCalifornia, United States4 46.120 September6.47.2×
San RafaelCalifornia, United States4 35.722 September4.27.1×
HollisterCalifornia, United States3 41.320 September5.87.1×
Redwood CityCalifornia, United States4 42.320 September6.07.1×
Santa CruzCalifornia, United States3 40.120 September5.86.9×
San FranciscoCalifornia, United States4 43.820 September6.46.8×
San LeandroCalifornia, United States4 43.020 September6.36.8×
GaltCalifornia, United States3 36.820 September5.66.6×
San Luis ObispoCalifornia, United States3 34.520 September5.46.4×
LompocCalifornia, United States4 32.321 September5.26.2×
SalinasCalifornia, United States5 43.620 September7.16.1×
San JoseCalifornia, United States3 47.720 September7.86.1×
FolsomCalifornia, United States3 31.820 September5.45.9×
SacramentoCalifornia, United States3 34.720 September6.05.8×
AtascaderoCalifornia, United States1 28.721 September4.55.7×
LincolnCalifornia, United States3 32.420 September5.75.7×
NipomoCalifornia, United States3 34.120 September6.05.7×
MantecaCalifornia, United States3 37.920 September6.95.5×
TracyCalifornia, United States1 27.422 September4.95.5×
DavisCalifornia, United States3 29.122 September5.45.4×
VacavilleCalifornia, United States2 26.822 September4.05.4×
Arroyo GrandeCalifornia, United States3 33.720 September6.35.3×
RosevilleCalifornia, United States2 31.820 September6.05.3×
StocktonCalifornia, United States3 37.120 September7.15.2×
UkiahCalifornia, United States3 29.822 September5.85.1×
OrcuttCalifornia, United States3 26.720 September5.44.9×
WoodlandCalifornia, United States3 33.520 September6.84.9×
MercedCalifornia, United States2 32.721 September6.94.7×
Yuba CityCalifornia, United States2 30.420 September6.74.5×
Arden-ArcadeCalifornia, United States2 32.220 September7.14.5×
ModestoCalifornia, United States3 32.222 September7.34.4×
RichmondCalifornia, United States5 40.320 September9.64.2×
TurlockCalifornia, United States4 31.122 September7.93.9×
MaderaCalifornia, United States3 35.021 September9.33.8×
ClovisCalifornia, United States1 33.621 September9.53.5×
Santa BarbaraCalifornia, United States1 26.322 September8.13.2×
FresnoCalifornia, United States3 34.021 September10.53.2×
TorranceCalifornia, United States3 26.924 September8.53.2×
Long BeachCalifornia, United States1 27.322 September8.83.1×
MexicaliBaja California, Mexico3 42.916 September14.23.0×
InglewoodCalifornia, United States1 26.324 September8.83.0×
OceansideCalifornia, United States1 26.423 September9.02.9×
CarsonCalifornia, United States3 26.724 September9.22.9×
CorcoranCalifornia, United States3 27.822 September9.72.9×
ComptonCalifornia, United States3 28.022 September9.82.9×
HanfordCalifornia, United States3 30.421 September10.82.8×
HawthorneCalifornia, United States1 26.724 September9.52.8×
Santa MonicaCalifornia, United States1 25.224 September9.12.8×
AnaheimCalifornia, United States2 26.523 September9.72.7×
PortervilleCalifornia, United States1 26.722 September10.12.6×
BakersfieldCalifornia, United States1 27.422 September10.92.5×
VisaliaCalifornia, United States3 26.622 September10.72.5×
FontanaCalifornia, United States2 28.923 September11.92.4×
Los AngelesCalifornia, United States1 26.424 September11.32.3×
TijuanaBaja California, Mexico1 29.327 September13.72.1×
Jurupa ValleyCalifornia, United States1 25.724 September12.42.1×

Daily means in µg/m³. Usual: the city's median for this time of year (its days within 21 days of the date, every year, leaving out the week around it). Above usual: its highest day against that.

Against other episodes in the United States and Mexico

Number 7 of 45 episodes in the United States and Mexico since our records began, by cities reached.

Bars: cities reached; colour: the level of the episode's highest daily reading. All 45.

Use this page

SmogRank, Western United States, September 2023: 61 cities with PM2.5 at twice their usual or more, 19 to 24 September 2023, smogrank.com/episodes/2023-09-western-united-states (accessed 2 October 2026).

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You're welcome to reuse a single chart, image or figure with this citation and a link. Terms.

An episode is a run of days when many cities close to each other (four or more within 350 km on a day, 8 or more in all) each had a daily PM2.5 mean of at least 25 µg/m³ and at least 2 times their usual for that time of year. Found in our own measurements, not picked by hand. How we find episodes. Values are each city's daily mean of its own monitors; causes are the usual kinds for a pattern like this, not a confirmed source.