SmogRank / Episodes / United States

California, United States, September 2023

For 6 days, from 19 to 24 September 2023, 59 cities in the United States 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 reached59in 1 country
Days619 to 24 September 2023
Worst day22 September49 cities counted
Furthest above usual8.8×Pleasanton

Day by day

22 September 49 cities at twice their usual or more
FillmoreSimi ValleyThousand OaksSanta ClaritaAgouraLancasterSouth Lake TahoeBurbankLa Crescenta-MontroseCarson CityLomitaTruckeeGlendoraRenoVictorvilleRiversideLake ElsinoreBanningPowaySan DiegoEl CajonIndioSummerlin SouthSpring ValleyEnterpriseBrawleyEl CentroJurupa ValleyLos AngelesFontanaVisaliaBakersfieldPortervilleSanta MonicaAnaheimHawthorneCorcoranHanfordOceansideCarsonComptonInglewoodLong BeachSanta BarbaraTorranceFresnoClovisMaderaTurlockRichmondModestoYuba CityArden-ArcadeMercedOrcuttWoodlandUkiahStocktonRosevilleArroyo GrandeVacavilleDavisTracyMantecaAtascaderoLincolnNipomoSacramentoFolsomSalinasSan JoseLompocSan Luis ObispoGaltSan LeandroSanta CruzSan RafaelHollisterRedwood CitySan FranciscoOaklandLivermoreConcordSanta 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

San FranciscoSan Francisco, 16 September: 8.7 µg/m³San Francisco, 17 September: 5.8 µg/m³San Francisco, 18 September: 6.5 µg/m³San Francisco, 19 September: 32.1 µg/m³, 5.1× its usual 6.3San Francisco, 20 September: 43.8 µg/m³, 7.1× its usual 6.2San Francisco, 21 September: 29.2 µg/m³, 4.9× its usual 6.0San Francisco, 22 September: 32.8 µg/m³, 5.7× its usual 5.8San Francisco, 23 September: 23.7 µg/m³San Francisco, 24 September: 4.9 µg/m³San Francisco, 25 September: 3.0 µg/m³San Francisco, 26 September: no readingSan Francisco, 27 September: no readingOaklandOakland, 16 September: 7.8 µg/m³Oakland, 17 September: 5.9 µg/m³Oakland, 18 September: 6.4 µg/m³Oakland, 19 September: 29.9 µg/m³, 4.7× its usual 6.4Oakland, 20 September: 46.1 µg/m³, 7.2× its usual 6.4Oakland, 21 September: 33.1 µg/m³, 5.3× its usual 6.2Oakland, 22 September: 34.2 µg/m³, 5.5× its usual 6.2Oakland, 23 September: 24.0 µg/m³Oakland, 24 September: 6.3 µg/m³Oakland, 25 September: 3.2 µg/m³Oakland, 26 September: 5.3 µg/m³Oakland, 27 September: 6.5 µg/m³RichmondRichmond, 16 September: 20.9 µg/m³Richmond, 17 September: 18.2 µg/m³Richmond, 18 September: 14.3 µg/m³Richmond, 19 September: 29.0 µg/m³, 3.0× its usual 9.8Richmond, 20 September: 40.3 µg/m³, 4.2× its usual 9.6Richmond, 21 September: 36.2 µg/m³, 3.8× its usual 9.5Richmond, 22 September: 35.9 µg/m³, 3.9× its usual 9.3Richmond, 23 September: 25.0 µg/m³, 2.7× its usual 9.2Richmond, 24 September: 7.5 µg/m³Richmond, 25 September: 5.6 µg/m³Richmond, 26 September: no readingRichmond, 27 September: no readingRedwood CityRedwood City, 16 September: 8.9 µg/m³Redwood City, 17 September: 7.5 µg/m³Redwood City, 18 September: 6.5 µg/m³Redwood City, 19 September: 27.8 µg/m³, 4.6× its usual 6.0Redwood City, 20 September: 42.3 µg/m³, 7.1× its usual 6.0Redwood City, 21 September: 33.3 µg/m³, 5.6× its usual 5.9Redwood City, 22 September: 31.1 µg/m³, 5.3× its usual 5.9Redwood City, 23 September: 23.0 µg/m³Redwood City, 24 September: 11.4 µg/m³Redwood City, 25 September: 4.6 µg/m³Redwood City, 26 September: 5.6 µg/m³Redwood City, 27 September: 7.3 µg/m³San LeandroSan Leandro, 16 September: 6.0 µg/m³San Leandro, 17 September: 4.8 µg/m³San Leandro, 18 September: 5.3 µg/m³San Leandro, 19 September: 26.2 µg/m³, 4.1× its usual 6.4San Leandro, 20 September: 43.0 µg/m³, 6.8× its usual 6.3San Leandro, 21 September: 31.0 µg/m³, 5.1× its usual 6.1San Leandro, 22 September: 32.0 µg/m³, 5.2× its usual 6.1San Leandro, 23 September: 21.4 µg/m³San Leandro, 24 September: 4.7 µg/m³San Leandro, 25 September: 2.2 µg/m³San Leandro, 26 September: 3.6 µg/m³San Leandro, 27 September: 4.3 µg/m³San RafaelSan Rafael, 16 September: 7.1 µg/m³San Rafael, 17 September: 4.9 µg/m³San Rafael, 18 September: 5.3 µg/m³San Rafael, 19 September: 25.6 µg/m³, 5.1× its usual 4.3San Rafael, 20 September: 31.5 µg/m³, 6.3× its usual 4.3San Rafael, 21 September: 29.3 µg/m³, 5.9× its usual 4.2San Rafael, 22 September: 35.7 µg/m³, 7.1× its usual 4.2San Rafael, 23 September: 21.3 µg/m³San Rafael, 24 September: 4.8 µg/m³San Rafael, 25 September: 2.8 µg/m³San Rafael, 26 September: 3.4 µg/m³San Rafael, 27 September: 4.3 µg/m³SalinasSalinas, 16 September: 11.0 µg/m³Salinas, 17 September: 10.7 µg/m³Salinas, 18 September: 8.7 µg/m³Salinas, 19 September: 25.4 µg/m³, 3.6× its usual 7.1Salinas, 20 September: 43.6 µg/m³, 6.1× its usual 7.1Salinas, 21 September: 34.6 µg/m³, 4.9× its usual 7.0Salinas, 22 September: 29.0 µg/m³, 4.1× its usual 7.0Salinas, 23 September: 26.5 µg/m³, 3.8× its usual 7.0Salinas, 24 September: 18.9 µg/m³Salinas, 25 September: 5.6 µg/m³Salinas, 26 September: 5.8 µg/m³Salinas, 27 September: 9.2 µg/m³San JoseSan Jose, 16 September: 9.3 µg/m³San Jose, 17 September: 6.7 µg/m³San Jose, 18 September: 6.2 µg/m³San Jose, 19 September: 22.7 µg/m³San Jose, 20 September: 47.7 µg/m³, 6.1× its usual 7.8San Jose, 21 September: 33.1 µg/m³, 4.3× its usual 7.7San Jose, 22 September: 33.3 µg/m³, 4.3× its usual 7.7San Jose, 23 September: 23.9 µg/m³San Jose, 24 September: 14.4 µg/m³San Jose, 25 September: 4.4 µg/m³San Jose, 26 September: 3.6 µg/m³San Jose, 27 September: 5.3 µg/m³PleasantonPleasanton, 16 September: no readingPleasanton, 17 September: no readingPleasanton, 18 September: no readingPleasanton, 19 September: 24.1 µg/m³Pleasanton, 20 September: 44.9 µg/m³, 8.8× its usual 5.1Pleasanton, 21 September: 34.0 µg/m³, 6.8× its usual 5.0Pleasanton, 22 September: 31.0 µg/m³, 6.2× its usual 5.0Pleasanton, 23 September: 25.2 µg/m³, 5.0× its usual 5.0Pleasanton, 24 September: 9.7 µg/m³Pleasanton, 25 September: 3.2 µg/m³Pleasanton, 26 September: 4.5 µg/m³Pleasanton, 27 September: 4.5 µg/m³LivermoreLivermore, 16 September: 7.8 µg/m³Livermore, 17 September: 4.6 µg/m³Livermore, 18 September: 5.4 µg/m³Livermore, 19 September: 20.4 µg/m³Livermore, 20 September: 43.0 µg/m³, 7.4× its usual 5.8Livermore, 21 September: 28.7 µg/m³, 5.0× its usual 5.7Livermore, 22 September: 28.0 µg/m³, 5.0× its usual 5.6Livermore, 23 September: 22.8 µg/m³Livermore, 24 September: 9.5 µg/m³Livermore, 25 September: 2.5 µg/m³Livermore, 26 September: 3.8 µg/m³Livermore, 27 September: 4.6 µg/m³GilroyGilroy, 16 September: 3.4 µg/m³Gilroy, 17 September: 3.5 µg/m³Gilroy, 18 September: 2.4 µg/m³Gilroy, 19 September: 10.6 µg/m³Gilroy, 20 September: 42.5 µg/m³, 8.5× its usual 4.6Gilroy, 21 September: 29.0 µg/m³, 5.8× its usual 4.5Gilroy, 22 September: 26.8 µg/m³, 5.4× its usual 4.4Gilroy, 23 September: 17.5 µg/m³Gilroy, 24 September: 13.5 µg/m³Gilroy, 25 September: 0.6 µg/m³Gilroy, 26 September: 2.0 µg/m³Gilroy, 27 September: 1.5 µg/m³Santa RosaSanta Rosa, 16 September: 3.9 µg/m³Santa Rosa, 17 September: 3.9 µg/m³Santa Rosa, 18 September: 4.5 µg/m³Santa Rosa, 19 September: 18.6 µg/m³Santa Rosa, 20 September: 41.4 µg/m³, 8.3× its usual 2.9Santa Rosa, 21 September: 38.3 µg/m³, 7.7× its usual 2.9Santa Rosa, 22 September: 33.4 µg/m³, 6.7× its usual 2.9Santa Rosa, 23 September: 17.9 µg/m³Santa Rosa, 24 September: 6.2 µg/m³Santa Rosa, 25 September: 1.4 µg/m³Santa Rosa, 26 September: 1.8 µg/m³Santa Rosa, 27 September: 1.6 µg/m³HollisterHollister, 16 September: 6.8 µg/m³Hollister, 17 September: 6.1 µg/m³Hollister, 18 September: 3.8 µg/m³Hollister, 19 September: 12.9 µg/m³Hollister, 20 September: 41.3 µg/m³, 7.1× its usual 5.8Hollister, 21 September: 31.6 µg/m³, 5.5× its usual 5.7Hollister, 22 September: 27.0 µg/m³, 4.8× its usual 5.6Hollister, 23 September: 18.9 µg/m³Hollister, 24 September: 14.1 µg/m³Hollister, 25 September: 3.1 µg/m³Hollister, 26 September: 2.6 µg/m³Hollister, 27 September: 4.4 µg/m³Santa CruzSanta Cruz, 16 September: 5.2 µg/m³Santa Cruz, 17 September: 5.5 µg/m³Santa Cruz, 18 September: 4.3 µg/m³Santa Cruz, 19 September: 13.0 µg/m³Santa Cruz, 20 September: 40.1 µg/m³, 6.9× its usual 5.8Santa Cruz, 21 September: 31.7 µg/m³, 5.6× its usual 5.7Santa Cruz, 22 September: 27.3 µg/m³, 5.0× its usual 5.5Santa Cruz, 23 September: 19.7 µg/m³Santa Cruz, 24 September: 11.6 µg/m³Santa Cruz, 25 September: 2.8 µg/m³Santa Cruz, 26 September: 3.4 µg/m³Santa Cruz, 27 September: 3.0 µg/m³ConcordConcord, 16 September: 6.5 µg/m³Concord, 17 September: 4.0 µg/m³Concord, 18 September: 3.3 µg/m³Concord, 19 September: 18.1 µg/m³Concord, 20 September: 39.3 µg/m³, 7.9× its usual 4.1Concord, 21 September: 29.5 µg/m³, 5.9× its usual 4.1Concord, 22 September: 29.9 µg/m³, 6.0× its usual 4.1Concord, 23 September: 20.8 µg/m³Concord, 24 September: 5.3 µg/m³Concord, 25 September: 2.4 µg/m³Concord, 26 September: 2.1 µg/m³Concord, 27 September: 2.7 µg/m³MantecaManteca, 16 September: 9.0 µg/m³Manteca, 17 September: 6.6 µg/m³Manteca, 18 September: 4.2 µg/m³Manteca, 19 September: 12.2 µg/m³Manteca, 20 September: 37.9 µg/m³, 5.5× its usual 6.9Manteca, 21 September: 26.7 µg/m³, 3.9× its usual 6.8Manteca, 22 September: 33.4 µg/m³, 4.9× its usual 6.8Manteca, 23 September: 24.8 µg/m³Manteca, 24 September: 15.5 µg/m³Manteca, 25 September: 4.3 µg/m³Manteca, 26 September: 4.3 µg/m³Manteca, 27 September: 4.4 µg/m³StocktonStockton, 16 September: 10.3 µg/m³Stockton, 17 September: 7.8 µg/m³Stockton, 18 September: 6.3 µg/m³Stockton, 19 September: 12.3 µg/m³Stockton, 20 September: 37.1 µg/m³, 5.2× its usual 7.1Stockton, 21 September: 26.0 µg/m³, 3.7× its usual 7.0Stockton, 22 September: 33.7 µg/m³, 4.8× its usual 7.0Stockton, 23 September: 23.9 µg/m³Stockton, 24 September: 15.1 µg/m³Stockton, 25 September: 5.4 µg/m³Stockton, 26 September: 5.9 µg/m³Stockton, 27 September: 5.9 µg/m³GaltGalt, 16 September: 8.9 µg/m³Galt, 17 September: 6.0 µg/m³Galt, 18 September: 4.4 µg/m³Galt, 19 September: 13.7 µg/m³Galt, 20 September: 36.8 µg/m³, 6.6× its usual 5.6Galt, 21 September: 26.0 µg/m³, 4.6× its usual 5.6Galt, 22 September: 30.5 µg/m³, 5.4× its usual 5.6Galt, 23 September: 21.7 µg/m³Galt, 24 September: 8.8 µg/m³Galt, 25 September: 2.6 µg/m³Galt, 26 September: 3.4 µg/m³Galt, 27 September: 4.1 µg/m³SacramentoSacramento, 16 September: 5.4 µg/m³Sacramento, 17 September: 5.1 µg/m³Sacramento, 18 September: 5.1 µg/m³Sacramento, 19 September: 13.1 µg/m³Sacramento, 20 September: 34.7 µg/m³, 5.8× its usual 6.0Sacramento, 21 September: 25.4 µg/m³, 4.3× its usual 5.9Sacramento, 22 September: 30.3 µg/m³, 5.1× its usual 6.0Sacramento, 23 September: 20.2 µg/m³Sacramento, 24 September: 7.8 µg/m³Sacramento, 25 September: 2.3 µg/m³Sacramento, 26 September: 3.2 µg/m³Sacramento, 27 September: 3.7 µg/m³San Luis ObispoSan Luis Obispo, 16 September: 8.7 µg/m³San Luis Obispo, 17 September: 6.8 µg/m³San Luis Obispo, 18 September: 4.8 µg/m³San Luis Obispo, 19 September: 7.9 µg/m³San Luis Obispo, 20 September: 34.5 µg/m³, 6.4× its usual 5.4San Luis Obispo, 21 September: 29.3 µg/m³, 5.6× its usual 5.2San Luis Obispo, 22 September: 28.7 µg/m³, 5.5× its usual 5.2San Luis Obispo, 23 September: 24.2 µg/m³San Luis Obispo, 24 September: 18.2 µg/m³San Luis Obispo, 25 September: 6.2 µg/m³San Luis Obispo, 26 September: 4.5 µg/m³San Luis Obispo, 27 September: 5.8 µg/m³NipomoNipomo, 16 September: 9.9 µg/m³Nipomo, 17 September: 7.0 µg/m³Nipomo, 18 September: 4.9 µg/m³Nipomo, 19 September: 9.7 µg/m³Nipomo, 20 September: 34.1 µg/m³, 5.7× its usual 6.0Nipomo, 21 September: 31.8 µg/m³, 5.4× its usual 5.9Nipomo, 22 September: 29.0 µg/m³, 5.0× its usual 5.8Nipomo, 23 September: 24.6 µg/m³Nipomo, 24 September: 19.6 µg/m³Nipomo, 25 September: 8.0 µg/m³Nipomo, 26 September: 12.5 µg/m³Nipomo, 27 September: 18.7 µg/m³Arroyo GrandeArroyo Grande, 16 September: 10.3 µg/m³Arroyo Grande, 17 September: 8.7 µg/m³Arroyo Grande, 18 September: 5.5 µg/m³Arroyo Grande, 19 September: 12.8 µg/m³Arroyo Grande, 20 September: 33.7 µg/m³, 5.3× its usual 6.3Arroyo Grande, 21 September: 32.1 µg/m³, 5.2× its usual 6.2Arroyo Grande, 22 September: 30.7 µg/m³, 5.0× its usual 6.1Arroyo Grande, 23 September: 24.7 µg/m³Arroyo Grande, 24 September: 19.5 µg/m³Arroyo Grande, 25 September: 8.6 µg/m³Arroyo Grande, 26 September: 12.5 µg/m³Arroyo Grande, 27 September: 16.4 µg/m³WoodlandWoodland, 16 September: 7.2 µg/m³Woodland, 17 September: 6.2 µg/m³Woodland, 18 September: 6.4 µg/m³Woodland, 19 September: 13.8 µg/m³Woodland, 20 September: 33.5 µg/m³, 4.9× its usual 6.8Woodland, 21 September: 26.9 µg/m³, 4.0× its usual 6.7Woodland, 22 September: 32.8 µg/m³, 4.8× its usual 6.8Woodland, 23 September: 21.8 µg/m³Woodland, 24 September: 8.9 µg/m³Woodland, 25 September: 3.3 µg/m³Woodland, 26 September: 2.5 µg/m³Woodland, 27 September: 5.1 µg/m³LincolnLincoln, 16 September: 9.3 µg/m³Lincoln, 17 September: 8.7 µg/m³Lincoln, 18 September: 7.3 µg/m³Lincoln, 19 September: 9.3 µg/m³Lincoln, 20 September: 32.4 µg/m³, 5.7× its usual 5.7Lincoln, 21 September: 25.2 µg/m³, 4.4× its usual 5.7Lincoln, 22 September: 27.3 µg/m³, 4.9× its usual 5.6Lincoln, 23 September: 20.2 µg/m³Lincoln, 24 September: 13.4 µg/m³Lincoln, 25 September: 3.3 µg/m³Lincoln, 26 September: no readingLincoln, 27 September: no readingArden-ArcadeArden-Arcade, 16 September: 4.3 µg/m³Arden-Arcade, 17 September: 3.2 µg/m³Arden-Arcade, 18 September: 2.9 µg/m³Arden-Arcade, 19 September: 10.2 µg/m³Arden-Arcade, 20 September: 32.2 µg/m³, 4.5× its usual 7.1Arden-Arcade, 21 September: 23.3 µg/m³Arden-Arcade, 22 September: 27.7 µg/m³, 4.1× its usual 6.7Arden-Arcade, 23 September: 18.6 µg/m³Arden-Arcade, 24 September: 8.1 µg/m³Arden-Arcade, 25 September: 1.2 µg/m³Arden-Arcade, 26 September: 0.5 µg/m³Arden-Arcade, 27 September: 2.3 µg/m³FolsomFolsom, 16 September: 7.5 µg/m³Folsom, 17 September: 6.8 µg/m³Folsom, 18 September: 5.1 µg/m³Folsom, 19 September: 9.7 µg/m³Folsom, 20 September: 31.8 µg/m³, 5.9× its usual 5.4Folsom, 21 September: 25.9 µg/m³, 4.9× its usual 5.3Folsom, 22 September: 27.3 µg/m³, 5.2× its usual 5.3Folsom, 23 September: 21.4 µg/m³Folsom, 24 September: 13.2 µg/m³Folsom, 25 September: 5.4 µg/m³Folsom, 26 September: 9.4 µg/m³Folsom, 27 September: 5.0 µg/m³RosevilleRoseville, 16 September: 8.6 µg/m³Roseville, 17 September: 6.9 µg/m³Roseville, 18 September: 7.2 µg/m³Roseville, 19 September: 10.6 µg/m³Roseville, 20 September: 31.8 µg/m³, 5.3× its usual 6.0Roseville, 21 September: 24.8 µg/m³Roseville, 22 September: 26.6 µg/m³, 4.5× its usual 5.9Roseville, 23 September: 20.5 µg/m³Roseville, 24 September: 13.0 µg/m³Roseville, 25 September: 3.7 µg/m³Roseville, 26 September: 2.6 µg/m³Roseville, 27 September: 4.5 µg/m³ModestoModesto, 16 September: 10.8 µg/m³Modesto, 17 September: 7.8 µg/m³Modesto, 18 September: 7.4 µg/m³Modesto, 19 September: 10.9 µg/m³Modesto, 20 September: 31.3 µg/m³, 4.3× its usual 7.3Modesto, 21 September: 25.8 µg/m³, 3.5× its usual 7.3Modesto, 22 September: 32.2 µg/m³, 4.4× its usual 7.3Modesto, 23 September: 24.7 µg/m³Modesto, 24 September: 18.3 µg/m³Modesto, 25 September: 6.0 µg/m³Modesto, 26 September: 4.7 µg/m³Modesto, 27 September: 6.2 µg/m³Yuba CityYuba City, 16 September: 9.8 µg/m³Yuba City, 17 September: 8.5 µg/m³Yuba City, 18 September: 8.5 µg/m³Yuba City, 19 September: 8.9 µg/m³Yuba City, 20 September: 30.4 µg/m³, 4.5× its usual 6.7Yuba City, 21 September: 19.1 µg/m³Yuba City, 22 September: 26.9 µg/m³, 4.1× its usual 6.6Yuba City, 23 September: 21.8 µg/m³Yuba City, 24 September: 15.3 µg/m³Yuba City, 25 September: 3.9 µg/m³Yuba City, 26 September: 3.7 µg/m³Yuba City, 27 September: 6.5 µg/m³LompocLompoc, 16 September: no readingLompoc, 17 September: no readingLompoc, 18 September: no readingLompoc, 19 September: 8.2 µg/m³Lompoc, 20 September: 30.0 µg/m³, 5.8× its usual 5.2Lompoc, 21 September: 32.3 µg/m³, 6.3× its usual 5.1Lompoc, 22 September: 29.0 µg/m³, 5.7× its usual 5.1Lompoc, 23 September: 25.8 µg/m³, 5.2× its usual 5.0Lompoc, 24 September: 18.7 µg/m³Lompoc, 25 September: 8.9 µg/m³Lompoc, 26 September: 4.7 µg/m³Lompoc, 27 September: 9.2 µg/m³TurlockTurlock, 16 September: 11.2 µg/m³Turlock, 17 September: 9.0 µg/m³Turlock, 18 September: 6.9 µg/m³Turlock, 19 September: 11.0 µg/m³Turlock, 20 September: 28.8 µg/m³, 3.6× its usual 8.0Turlock, 21 September: 28.4 µg/m³, 3.6× its usual 8.0Turlock, 22 September: 31.1 µg/m³, 3.9× its usual 8.0Turlock, 23 September: 26.8 µg/m³, 3.4× its usual 8.0Turlock, 24 September: 19.6 µg/m³Turlock, 25 September: 6.7 µg/m³Turlock, 26 September: 6.8 µg/m³Turlock, 27 September: 7.1 µg/m³DavisDavis, 16 September: 8.4 µg/m³Davis, 17 September: 7.1 µg/m³Davis, 18 September: 6.4 µg/m³Davis, 19 September: 15.3 µg/m³Davis, 20 September: 28.7 µg/m³, 5.2× its usual 5.5Davis, 21 September: 27.4 µg/m³, 5.0× its usual 5.5Davis, 22 September: 29.1 µg/m³, 5.4× its usual 5.4Davis, 23 September: 21.9 µg/m³Davis, 24 September: 8.2 µg/m³Davis, 25 September: 2.9 µg/m³Davis, 26 September: 2.6 µg/m³Davis, 27 September: 4.1 µg/m³OrcuttOrcutt, 16 September: 5.5 µg/m³Orcutt, 17 September: 4.9 µg/m³Orcutt, 18 September: 3.4 µg/m³Orcutt, 19 September: 6.7 µg/m³Orcutt, 20 September: 26.7 µg/m³, 4.9× its usual 5.4Orcutt, 21 September: 25.0 µg/m³, 4.8× its usual 5.2Orcutt, 22 September: 25.0 µg/m³, 5.0× its usual 5.0Orcutt, 23 September: 21.7 µg/m³Orcutt, 24 September: 17.3 µg/m³Orcutt, 25 September: 6.4 µg/m³Orcutt, 26 September: 4.5 µg/m³Orcutt, 27 September: 5.9 µg/m³VacavilleVacaville, 16 September: 3.8 µg/m³Vacaville, 17 September: 3.1 µg/m³Vacaville, 18 September: 3.7 µg/m³Vacaville, 19 September: 13.2 µg/m³Vacaville, 20 September: 26.3 µg/m³, 5.3× its usual 4.1Vacaville, 21 September: 21.7 µg/m³Vacaville, 22 September: 26.8 µg/m³, 5.4× its usual 4.1Vacaville, 23 September: 16.9 µg/m³Vacaville, 24 September: 6.1 µg/m³Vacaville, 25 September: 2.5 µg/m³Vacaville, 26 September: 2.5 µg/m³Vacaville, 27 September: 2.1 µg/m³UkiahUkiah, 16 September: 5.5 µg/m³Ukiah, 17 September: 4.5 µg/m³Ukiah, 18 September: 5.9 µg/m³Ukiah, 19 September: 10.5 µg/m³Ukiah, 20 September: 25.1 µg/m³, 4.3× its usual 5.8Ukiah, 21 September: 27.4 µg/m³, 4.8× its usual 5.7Ukiah, 22 September: 29.8 µg/m³, 5.1× its usual 5.8Ukiah, 23 September: no readingUkiah, 24 September: no readingUkiah, 25 September: no readingUkiah, 26 September: no readingUkiah, 27 September: 7.9 µg/m³MaderaMadera, 16 September: 13.7 µg/m³Madera, 17 September: 11.9 µg/m³Madera, 18 September: 9.0 µg/m³Madera, 19 September: 8.7 µg/m³Madera, 20 September: 18.9 µg/m³Madera, 21 September: 35.0 µg/m³, 3.8× its usual 9.3Madera, 22 September: 27.8 µg/m³, 3.0× its usual 9.2Madera, 23 September: 27.5 µg/m³, 3.0× its usual 9.1Madera, 24 September: 21.4 µg/m³Madera, 25 September: 8.5 µg/m³Madera, 26 September: 6.5 µg/m³Madera, 27 September: 7.4 µg/m³FresnoFresno, 16 September: 11.5 µg/m³Fresno, 17 September: 10.0 µg/m³Fresno, 18 September: 8.2 µg/m³Fresno, 19 September: 8.3 µg/m³Fresno, 20 September: 15.9 µg/m³Fresno, 21 September: 34.0 µg/m³, 3.2× its usual 10.6Fresno, 22 September: 28.0 µg/m³, 2.7× its usual 10.3Fresno, 23 September: 25.7 µg/m³, 2.5× its usual 10.3Fresno, 24 September: 22.3 µg/m³Fresno, 25 September: 11.8 µg/m³Fresno, 26 September: 5.6 µg/m³Fresno, 27 September: 7.2 µg/m³ClovisClovis, 16 September: 11.1 µg/m³Clovis, 17 September: 8.2 µg/m³Clovis, 18 September: 6.1 µg/m³Clovis, 19 September: 7.4 µg/m³Clovis, 20 September: 13.5 µg/m³Clovis, 21 September: 33.6 µg/m³, 3.5× its usual 9.5Clovis, 22 September: 24.7 µg/m³Clovis, 23 September: 23.6 µg/m³Clovis, 24 September: 22.3 µg/m³Clovis, 25 September: 9.1 µg/m³Clovis, 26 September: 3.6 µg/m³Clovis, 27 September: 5.2 µg/m³MercedMerced, 16 September: 8.9 µg/m³Merced, 17 September: 7.0 µg/m³Merced, 18 September: 5.1 µg/m³Merced, 19 September: 6.1 µg/m³Merced, 20 September: 18.6 µg/m³Merced, 21 September: 32.7 µg/m³, 4.7× its usual 7.0Merced, 22 September: 25.8 µg/m³, 3.7× its usual 7.0Merced, 23 September: 24.5 µg/m³Merced, 24 September: 17.0 µg/m³Merced, 25 September: 4.6 µg/m³Merced, 26 September: 2.9 µg/m³Merced, 27 September: 4.9 µg/m³HanfordHanford, 16 September: 11.5 µg/m³Hanford, 17 September: 8.9 µg/m³Hanford, 18 September: 9.3 µg/m³Hanford, 19 September: 9.0 µg/m³Hanford, 20 September: 18.2 µg/m³Hanford, 21 September: 30.4 µg/m³, 2.8× its usual 11.0Hanford, 22 September: 29.0 µg/m³, 2.7× its usual 10.8Hanford, 23 September: 26.5 µg/m³, 2.5× its usual 10.8Hanford, 24 September: 23.5 µg/m³Hanford, 25 September: 10.1 µg/m³Hanford, 26 September: 6.1 µg/m³Hanford, 27 September: 6.2 µg/m³AtascaderoAtascadero, 16 September: 7.1 µg/m³Atascadero, 17 September: 5.1 µg/m³Atascadero, 18 September: 3.5 µg/m³Atascadero, 19 September: 6.8 µg/m³Atascadero, 20 September: 23.3 µg/m³Atascadero, 21 September: 28.7 µg/m³, 5.7× its usual 4.5Atascadero, 22 September: 24.0 µg/m³Atascadero, 23 September: 19.3 µg/m³Atascadero, 24 September: 14.8 µg/m³Atascadero, 25 September: 7.4 µg/m³Atascadero, 26 September: 2.5 µg/m³Atascadero, 27 September: 3.4 µg/m³VisaliaVisalia, 16 September: 13.6 µg/m³Visalia, 17 September: 9.4 µg/m³Visalia, 18 September: 7.3 µg/m³Visalia, 19 September: 9.6 µg/m³Visalia, 20 September: 13.0 µg/m³Visalia, 21 September: 25.4 µg/m³, 2.4× its usual 10.8Visalia, 22 September: 26.6 µg/m³, 2.5× its usual 10.7Visalia, 23 September: 25.8 µg/m³, 2.4× its usual 10.7Visalia, 24 September: 24.4 µg/m³Visalia, 25 September: 14.8 µg/m³Visalia, 26 September: 6.5 µg/m³Visalia, 27 September: 7.6 µg/m³CorcoranCorcoran, 16 September: 11.7 µg/m³Corcoran, 17 September: 8.9 µg/m³Corcoran, 18 September: 6.5 µg/m³Corcoran, 19 September: 8.3 µg/m³Corcoran, 20 September: 14.2 µg/m³Corcoran, 21 September: 25.2 µg/m³, 2.5× its usual 10.0Corcoran, 22 September: 27.8 µg/m³, 2.8× its usual 9.8Corcoran, 23 September: 25.1 µg/m³, 2.6× its usual 9.7Corcoran, 24 September: 21.7 µg/m³Corcoran, 25 September: 10.8 µg/m³Corcoran, 26 September: 4.8 µg/m³Corcoran, 27 September: 6.2 µg/m³ComptonCompton, 16 September: 10.4 µg/m³Compton, 17 September: 6.5 µg/m³Compton, 18 September: 10.1 µg/m³Compton, 19 September: 9.8 µg/m³Compton, 20 September: 12.7 µg/m³Compton, 21 September: 21.2 µg/m³Compton, 22 September: 28.0 µg/m³, 2.9× its usual 9.8Compton, 23 September: 25.8 µg/m³, 2.6× its usual 9.8Compton, 24 September: 26.8 µg/m³, 2.7× its usual 9.9Compton, 25 September: 21.3 µg/m³Compton, 26 September: 12.3 µg/m³Compton, 27 September: 13.6 µg/m³TracyTracy, 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/m³Tracy, 22 September: 27.4 µg/m³, 5.5× its usual 4.9Tracy, 23 September: 22.9 µg/m³Tracy, 24 September: 12.6 µg/m³Tracy, 25 September: 2.0 µg/m³Tracy, 26 September: 2.8 µg/m³Tracy, 27 September: 2.6 µg/m³BakersfieldBakersfield, 16 September: 12.7 µg/m³Bakersfield, 17 September: 9.9 µg/m³Bakersfield, 18 September: 6.8 µg/m³Bakersfield, 19 September: 11.4 µg/m³Bakersfield, 20 September: 14.4 µg/m³Bakersfield, 21 September: 21.0 µg/m³Bakersfield, 22 September: 27.4 µg/m³, 2.5× its usual 10.9Bakersfield, 23 September: 24.3 µg/m³Bakersfield, 24 September: 21.3 µg/m³Bakersfield, 25 September: 16.6 µg/m³Bakersfield, 26 September: 10.9 µg/m³Bakersfield, 27 September: 11.7 µg/m³Long BeachLong Beach, 16 September: 10.7 µg/m³Long Beach, 17 September: 11.8 µg/m³Long Beach, 18 September: 12.5 µg/m³Long Beach, 19 September: 8.4 µg/m³Long Beach, 20 September: 10.3 µg/m³Long Beach, 21 September: 17.9 µg/m³Long Beach, 22 September: 27.3 µg/m³, 3.1× its usual 8.8Long Beach, 23 September: 23.2 µg/m³Long Beach, 24 September: 22.9 µg/m³Long Beach, 25 September: 19.4 µg/m³Long Beach, 26 September: 10.9 µg/m³Long Beach, 27 September: 9.9 µg/m³PortervillePorterville, 16 September: 14.1 µg/m³Porterville, 17 September: 10.5 µg/m³Porterville, 18 September: 8.4 µg/m³Porterville, 19 September: 12.0 µg/m³Porterville, 20 September: 13.3 µg/m³Porterville, 21 September: 24.5 µg/m³Porterville, 22 September: 26.7 µg/m³, 2.6× its usual 10.1Porterville, 23 September: 23.6 µg/m³Porterville, 24 September: 20.2 µg/m³Porterville, 25 September: 18.0 µg/m³Porterville, 26 September: 9.9 µg/m³Porterville, 27 September: 10.0 µg/m³Santa BarbaraSanta Barbara, 16 September: 9.0 µg/m³Santa Barbara, 17 September: 7.6 µg/m³Santa Barbara, 18 September: 7.5 µg/m³Santa Barbara, 19 September: 6.5 µg/m³Santa Barbara, 20 September: 15.3 µg/m³Santa Barbara, 21 September: 22.5 µg/m³Santa Barbara, 22 September: 26.3 µg/m³, 3.2× its usual 8.1Santa Barbara, 23 September: 24.5 µg/m³Santa Barbara, 24 September: 21.3 µg/m³Santa Barbara, 25 September: 14.3 µg/m³Santa Barbara, 26 September: 8.5 µg/m³Santa Barbara, 27 September: 8.0 µg/m³TorranceTorrance, 16 September: 8.5 µg/m³Torrance, 17 September: 6.8 µg/m³Torrance, 18 September: 7.9 µg/m³Torrance, 19 September: 8.7 µg/m³Torrance, 20 September: 11.9 µg/m³Torrance, 21 September: 19.4 µg/m³Torrance, 22 September: 25.9 µg/m³, 3.0× its usual 8.5Torrance, 23 September: 25.4 µg/m³, 3.0× its usual 8.6Torrance, 24 September: 26.9 µg/m³, 3.2× its usual 8.5Torrance, 25 September: 22.2 µg/m³Torrance, 26 September: 10.8 µg/m³Torrance, 27 September: 8.7 µg/m³CarsonCarson, 16 September: 8.4 µg/m³Carson, 17 September: 6.7 µg/m³Carson, 18 September: 8.0 µg/m³Carson, 19 September: 9.0 µg/m³Carson, 20 September: 11.4 µg/m³Carson, 21 September: 19.7 µg/m³Carson, 22 September: 25.8 µg/m³, 2.7× its usual 9.4Carson, 23 September: 25.3 µg/m³, 2.7× its usual 9.3Carson, 24 September: 26.7 µg/m³, 2.9× its usual 9.2Carson, 25 September: 21.4 µg/m³Carson, 26 September: 10.9 µg/m³Carson, 27 September: 9.4 µg/m³FontanaFontana, 16 September: 25.6 µg/m³Fontana, 17 September: 16.5 µg/m³Fontana, 18 September: 11.8 µg/m³Fontana, 19 September: 13.3 µg/m³Fontana, 20 September: 11.7 µg/m³Fontana, 21 September: 16.6 µg/m³Fontana, 22 September: 22.2 µg/m³Fontana, 23 September: 28.9 µg/m³, 2.4× its usual 11.9Fontana, 24 September: 27.2 µg/m³, 2.2× its usual 12.2Fontana, 25 September: 28.5 µg/m³Fontana, 26 September: 20.5 µg/m³Fontana, 27 September: 18.9 µg/m³AnaheimAnaheim, 16 September: 12.6 µg/m³Anaheim, 17 September: 6.0 µg/m³Anaheim, 18 September: 8.2 µg/m³Anaheim, 19 September: 9.0 µg/m³Anaheim, 20 September: 11.3 µg/m³Anaheim, 21 September: 18.8 µg/m³Anaheim, 22 September: 23.8 µg/m³Anaheim, 23 September: 26.5 µg/m³, 2.7× its usual 9.7Anaheim, 24 September: 26.0 µg/m³, 2.7× its usual 9.7Anaheim, 25 September: 23.3 µg/m³Anaheim, 26 September: 15.9 µg/m³Anaheim, 27 September: 13.4 µg/m³OceansideOceanside, 16 September: 6.1 µg/m³Oceanside, 17 September: 5.9 µg/m³Oceanside, 18 September: 7.1 µg/m³Oceanside, 19 September: 7.2 µg/m³Oceanside, 20 September: 10.4 µg/m³Oceanside, 21 September: 16.7 µg/m³Oceanside, 22 September: 18.5 µg/m³Oceanside, 23 September: 26.4 µg/m³, 2.9× its usual 9.0Oceanside, 24 September: 23.9 µg/m³Oceanside, 25 September: 21.1 µg/m³Oceanside, 26 September: 13.0 µg/m³Oceanside, 27 September: 11.3 µg/m³HawthorneHawthorne, 16 September: 8.8 µg/m³Hawthorne, 17 September: 6.9 µg/m³Hawthorne, 18 September: 8.0 µg/m³Hawthorne, 19 September: 10.0 µg/m³Hawthorne, 20 September: 10.6 µg/m³Hawthorne, 21 September: 18.9 µg/m³Hawthorne, 22 September: 24.2 µg/m³Hawthorne, 23 September: 23.5 µg/m³Hawthorne, 24 September: 26.7 µg/m³, 2.8× its usual 9.5Hawthorne, 25 September: 20.0 µg/m³Hawthorne, 26 September: 10.5 µg/m³Hawthorne, 27 September: 10.3 µg/m³Los AngelesLos Angeles, 16 September: 9.9 µg/m³Los Angeles, 17 September: 5.8 µg/m³Los Angeles, 18 September: 7.3 µg/m³Los Angeles, 19 September: 11.3 µg/m³Los Angeles, 20 September: 9.3 µg/m³Los Angeles, 21 September: 19.2 µg/m³Los Angeles, 22 September: 21.9 µg/m³Los Angeles, 23 September: 24.6 µg/m³Los Angeles, 24 September: 26.4 µg/m³, 2.3× its usual 11.3Los Angeles, 25 September: 22.9 µg/m³Los Angeles, 26 September: 14.4 µg/m³Los Angeles, 27 September: 12.8 µg/m³InglewoodInglewood, 16 September: 8.7 µg/m³Inglewood, 17 September: 6.7 µg/m³Inglewood, 18 September: 7.6 µg/m³Inglewood, 19 September: 9.7 µg/m³Inglewood, 20 September: 11.0 µg/m³Inglewood, 21 September: 18.1 µg/m³Inglewood, 22 September: 21.0 µg/m³Inglewood, 23 September: 24.0 µg/m³Inglewood, 24 September: 26.3 µg/m³, 3.0× its usual 8.8Inglewood, 25 September: 20.2 µg/m³Inglewood, 26 September: 11.9 µg/m³Inglewood, 27 September: 9.0 µg/m³Jurupa ValleyJurupa Valley, 16 September: 21.8 µg/m³Jurupa Valley, 17 September: 9.2 µg/m³Jurupa Valley, 18 September: 8.5 µg/m³Jurupa Valley, 19 September: 10.5 µg/m³Jurupa Valley, 20 September: 9.3 µg/m³Jurupa Valley, 21 September: 14.0 µg/m³Jurupa Valley, 22 September: 20.9 µg/m³Jurupa Valley, 23 September: 24.5 µg/m³Jurupa Valley, 24 September: 25.7 µg/m³, 2.0× its usual 12.6Jurupa Valley, 25 September: 25.1 µg/m³Jurupa Valley, 26 September: 18.9 µg/m³Jurupa Valley, 27 September: 15.4 µg/m³Santa MonicaSanta Monica, 16 September: 8.4 µg/m³Santa Monica, 17 September: 7.1 µg/m³Santa Monica, 18 September: 7.9 µg/m³Santa Monica, 19 September: 10.2 µg/m³Santa Monica, 20 September: 10.5 µg/m³Santa Monica, 21 September: 16.7 µg/m³Santa Monica, 22 September: 19.9 µg/m³Santa Monica, 23 September: 23.6 µg/m³Santa Monica, 24 September: 25.2 µg/m³, 2.7× its usual 9.2Santa Monica, 25 September: 20.3 µg/m³Santa Monica, 26 September: 10.9 µg/m³Santa Monica, 27 September: 8.8 µg/m³16 Sep1820222426
Every counted city, 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 September5.87.4×
OaklandCalifornia, United States4 46.120 September6.47.2×
San FranciscoCalifornia, United States4 43.820 September6.27.1×
Redwood CityCalifornia, United States4 42.320 September6.07.1×
HollisterCalifornia, United States3 41.320 September5.87.1×
San RafaelCalifornia, United States4 35.722 September4.27.1×
Santa CruzCalifornia, United States3 40.120 September5.86.9×
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 September5.16.3×
San JoseCalifornia, United States3 47.720 September7.86.1×
SalinasCalifornia, United States5 43.620 September7.16.1×
FolsomCalifornia, United States3 31.820 September5.45.9×
SacramentoCalifornia, United States3 34.720 September6.05.8×
NipomoCalifornia, United States3 34.120 September6.05.7×
LincolnCalifornia, United States3 32.420 September5.75.7×
AtascaderoCalifornia, United States1 28.721 September4.55.7×
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 September4.15.4×
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×
WoodlandCalifornia, United States3 33.520 September6.84.9×
OrcuttCalifornia, United States3 26.720 September5.44.9×
MercedCalifornia, United States2 32.721 September7.04.7×
Arden-ArcadeCalifornia, United States2 32.220 September7.14.5×
Yuba CityCalifornia, United States2 30.420 September6.74.5×
ModestoCalifornia, United States3 32.222 September7.34.4×
RichmondCalifornia, United States5 40.320 September9.64.2×
TurlockCalifornia, United States4 31.122 September8.03.9×
MaderaCalifornia, United States3 35.021 September9.33.8×
ClovisCalifornia, United States1 33.621 September9.53.5×
FresnoCalifornia, United States3 34.021 September10.63.2×
TorranceCalifornia, United States3 26.924 September8.53.2×
Santa BarbaraCalifornia, United States1 26.322 September8.13.2×
Long BeachCalifornia, United States1 27.322 September8.83.1×
InglewoodCalifornia, United States1 26.324 September8.83.0×
ComptonCalifornia, United States3 28.022 September9.82.9×
CarsonCalifornia, United States3 26.724 September9.22.9×
OceansideCalifornia, United States1 26.423 September9.02.9×
HanfordCalifornia, United States3 30.421 September11.02.8×
CorcoranCalifornia, United States3 27.822 September9.82.8×
HawthorneCalifornia, United States1 26.724 September9.52.8×
AnaheimCalifornia, United States2 26.523 September9.72.7×
Santa MonicaCalifornia, United States1 25.224 September9.22.7×
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×
Jurupa ValleyCalifornia, United States1 25.724 September12.62.0×

Daily means in µg/m³, over the days each city counted in this episode. Highest: its highest of those days. Usual: the city's median for the time of year of that day (its days within 21 days of the date, every year, leaving out the week around it). Above usual: its highest day against that, with a usual under 5 µg/m³ taken as 5.

Against other episodes in the United States

Number 17 of 130 episodes in the United States since our records began, by cities reached.

Bars: cities reached; colour: the level of the episode's highest daily reading. All 130.

Use this page

SmogRank, California, United States, September 2023: 59 cities with PM2.5 at twice their usual or more, 19 to 24 September 2023, smogrank.com/episodes/2023-09-california-united-states (accessed 4 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.