SmogRank / Episodes / United States

California, United States, 26 to 27 January 2026

For 2 days, from 26 to 27 January 2026, 9 cities in the United States had PM2.5 at least twice their usual for the time of year. The worst reading was Bakersfield, California, United States: 44.0 µg/m³ on 27 January, about 3.5× its usual 12.4. Ended 27 January.

No cause namedWe have no fire or smoke records for these days, so we only say what the measurements show.
Cities reached9in 1 country
Days226 to 27 January 2026
Worst day27 January6 cities counted
Furthest above usual5.8×Sunnyvale

Day by day

27 January 6 cities at twice their usual or more
MercedTurlockMaderaMantecaStocktonTracyHollisterFresnoClovisGilroyGaltLivermorePrunedaleRancho MurietaHuronWatsonvilleSalinasKing CityElk GroveSan JosePleasantonFlorinHanfordFolsomLive OakSeasideSanta CruzMountain ViewSacramentoBen LomondRosevilleConcordSan LeandroCorcoranMammoth LakesNorth AuburnDavisVisaliaRedwood CitySouth Lake TahoeLincolnMartinezTulareVacavilleOaklandBerkeleyVallejoAlta SierraSouth San FranciscoRichmondAtascaderoSan FranciscoCarson CityTruckeePortervilleSan RafaelYuba CityDelanoSan Luis ObispoArroyo GrandeOceanoRenoNipomoColusaGuadalupeSpanish SpringsSebastopolWindsorParadiseChicoWillowsUkiahRidgecrestModestoRio VistaArden-ArcadeFremontBakersfieldWoodlandGridleyPalo AltoSunnyvale
23 Jan24252627282930
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

FremontFremont, 23 January: 31.6 µg/m³Fremont, 24 January: 12.4 µg/m³Fremont, 25 January: 16.5 µg/m³Fremont, 26 January: 35.3 µg/m³, 3.5× its usual 10.2Fremont, 27 January: 14.9 µg/m³Fremont, 28 January: 6.4 µg/m³Fremont, 29 January: 10.7 µg/m³Fremont, 30 January: 23.7 µg/m³SunnyvaleSunnyvale, 23 January: 26.8 µg/m³Sunnyvale, 24 January: 11.6 µg/m³Sunnyvale, 25 January: 9.9 µg/m³Sunnyvale, 26 January: 29.1 µg/m³, 5.8× its usual 4.6Sunnyvale, 27 January: 6.0 µg/m³Sunnyvale, 28 January: 4.7 µg/m³Sunnyvale, 29 January: 4.6 µg/m³Sunnyvale, 30 January: 19.5 µg/m³Palo AltoPalo Alto, 23 January: 26.6 µg/m³Palo Alto, 24 January: 12.9 µg/m³Palo Alto, 25 January: 11.7 µg/m³Palo Alto, 26 January: 27.6 µg/m³, 5.5× its usual 4.0Palo Alto, 27 January: 13.1 µg/m³Palo Alto, 28 January: 6.5 µg/m³Palo Alto, 29 January: 5.7 µg/m³Palo Alto, 30 January: 18.3 µg/m³ModestoModesto, 23 January: 22.6 µg/m³Modesto, 24 January: 20.1 µg/m³Modesto, 25 January: 21.6 µg/m³Modesto, 26 January: 27.5 µg/m³, 2.5× its usual 10.8Modesto, 27 January: 28.4 µg/m³, 2.6× its usual 10.8Modesto, 28 January: 21.2 µg/m³Modesto, 29 January: 17.2 µg/m³Modesto, 30 January: 28.5 µg/m³BakersfieldBakersfield, 23 January: 19.8 µg/m³Bakersfield, 24 January: 14.6 µg/m³Bakersfield, 25 January: 19.5 µg/m³Bakersfield, 26 January: 23.8 µg/m³Bakersfield, 27 January: 44.0 µg/m³, 3.5× its usual 12.4Bakersfield, 28 January: 32.3 µg/m³Bakersfield, 29 January: 24.9 µg/m³Bakersfield, 30 January: 34.3 µg/m³GridleyGridley, 23 January: 12.7 µg/m³Gridley, 24 January: 4.8 µg/m³Gridley, 25 January: 15.6 µg/m³Gridley, 26 January: 14.0 µg/m³Gridley, 27 January: 26.8 µg/m³, 4.3× its usual 6.3Gridley, 28 January: 12.4 µg/m³Gridley, 29 January: 7.9 µg/m³Gridley, 30 January: 13.9 µg/m³WoodlandWoodland, 23 January: 22.4 µg/m³Woodland, 24 January: 10.4 µg/m³Woodland, 25 January: no readingWoodland, 26 January: no readingWoodland, 27 January: 25.7 µg/m³, 3.6× its usual 7.2Woodland, 28 January: 15.9 µg/m³Woodland, 29 January: 10.6 µg/m³Woodland, 30 January: 16.0 µg/m³Arden-ArcadeArden-Arcade, 23 January: 23.3 µg/m³Arden-Arcade, 24 January: 10.0 µg/m³Arden-Arcade, 25 January: 17.0 µg/m³Arden-Arcade, 26 January: 16.9 µg/m³Arden-Arcade, 27 January: 25.6 µg/m³, 2.8× its usual 9.1Arden-Arcade, 28 January: 11.9 µg/m³Arden-Arcade, 29 January: 11.6 µg/m³Arden-Arcade, 30 January: 19.9 µg/m³Rio VistaRio Vista, 23 January: 23.5 µg/m³Rio Vista, 24 January: 15.8 µg/m³Rio Vista, 25 January: 20.3 µg/m³Rio Vista, 26 January: 22.5 µg/m³Rio Vista, 27 January: 25.3 µg/m³, 2.7× its usual 9.3Rio Vista, 28 January: 17.8 µg/m³Rio Vista, 29 January: 16.1 µg/m³Rio Vista, 30 January: 23.5 µg/m³23 Jan24252627282930
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
SunnyvaleCalifornia, United States1 29.126 January4.65.8×
Palo AltoCalifornia, United States1 27.626 January4.05.5×
GridleyCalifornia, United States1 26.827 January6.34.3×
WoodlandCalifornia, United States1 25.727 January7.23.6×
BakersfieldCalifornia, United States1 44.027 January12.43.5×
FremontCalifornia, United States1 35.326 January10.23.5×
Arden-ArcadeCalifornia, United States1 25.627 January9.12.8×
Rio VistaCalifornia, United States1 25.327 January9.32.7×
ModestoCalifornia, United States2 28.427 January10.82.6×

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 130 of 151 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 151.

Use this page

SmogRank, California, United States, 26 to 27 January 2026: 9 cities with PM2.5 at twice their usual or more, 26 to 27 January 2026, smogrank.com/episodes/2026-01-26-california-united-states (accessed 5 October 2026).

Download top 10 (PNG)

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.