SmogRank / Episodes / United States
California and Oregon, United States, January 2026
For 5 days, from 13 to 17 January 2026, 23 cities in the United States had PM2.5 at least twice their usual for the time of year. The worst reading was Fresno, California, United States: 47.3 µg/m³ on 14 January, about 3.0× its usual 15.7.
No cause named We have no fire or smoke records for these days, so we only say what the measurements show.
Cities reached 23 in 1 country
Days 5 13 to 17 January 2026
Worst day 15 January 18 cities counted
Furthest above usual 4.0× Sacramento
Day by day
Play 15 January 18 cities at twice their usual or more
Folsom Lincoln Roseville Elk Grove Galt Davis Truckee South Lake Tahoe Paradise Vacaville Tracy Carson City Reno Turlock Concord Livermore Martinez Spanish Springs Pleasanton Berkeley San Leandro Richmond San Jose San Rafael Santa Rosa San Francisco Sunnyvale Palo Alto Mountain View Redwood City Windsor Gilroy Hollister Watsonville Live Oak Santa Cruz Prunedale Redding Ukiah Salinas Seaside Tulare Atascadero Altamont Delano San Luis Obispo Arroyo Grande Ashland Nipomo Orcutt Grants Pass Ridgecrest Florin Fremont Merced Medford Stockton Visalia Clovis Vallejo Corcoran Hanford Bakersfield Fresno Manteca Chico Madera Porterville Modesto Arden-Arcade Oakland Woodland South San Francisco Yuba City Sacramento 10 Jan 11 12 13 14 15 16 17 18 19 20 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
Bakersfield Bakersfield, 10 January: 20.7 µg/m³ Bakersfield, 11 January: 29.9 µg/m³ Bakersfield, 12 January: 31.4 µg/m³ Bakersfield, 13 January: 34.7 µg/m³, 2.4× its usual 14.6 Bakersfield, 14 January: 40.5 µg/m³, 3.0× its usual 13.6 Bakersfield, 15 January: 40.4 µg/m³, 3.0× its usual 13.5 Bakersfield, 16 January: 37.7 µg/m³, 2.8× its usual 13.3 Bakersfield, 17 January: 30.1 µg/m³, 2.3× its usual 13.3 Bakersfield, 18 January: 30.0 µg/m³ Bakersfield, 19 January: 25.4 µg/m³ Bakersfield, 20 January: 20.8 µg/m³ Visalia Visalia, 10 January: 17.5 µg/m³ Visalia, 11 January: 26.9 µg/m³ Visalia, 12 January: 29.2 µg/m³ Visalia, 13 January: 34.1 µg/m³, 2.3× its usual 14.7 Visalia, 14 January: 37.6 µg/m³, 2.6× its usual 14.2 Visalia, 15 January: 37.0 µg/m³, 2.6× its usual 14.0 Visalia, 16 January: 34.5 µg/m³, 2.6× its usual 13.2 Visalia, 17 January: 23.8 µg/m³ Visalia, 18 January: 19.6 µg/m³ Visalia, 19 January: 16.4 µg/m³ Visalia, 20 January: 14.0 µg/m³ Modesto Modesto, 10 January: 16.8 µg/m³ Modesto, 11 January: 28.5 µg/m³ Modesto, 12 January: 22.9 µg/m³ Modesto, 13 January: 33.9 µg/m³, 2.9× its usual 11.5 Modesto, 14 January: 32.6 µg/m³, 2.9× its usual 11.4 Modesto, 15 January: 33.8 µg/m³, 3.0× its usual 11.2 Modesto, 16 January: 37.1 µg/m³, 3.3× its usual 11.1 Modesto, 17 January: 28.7 µg/m³, 2.6× its usual 11.1 Modesto, 18 January: 24.2 µg/m³ Modesto, 19 January: 18.8 µg/m³ Modesto, 20 January: 16.5 µg/m³ Fresno Fresno, 10 January: 22.3 µg/m³ Fresno, 11 January: 29.3 µg/m³ Fresno, 12 January: 24.1 µg/m³ Fresno, 13 January: 33.8 µg/m³, 2.1× its usual 16.0 Fresno, 14 January: 47.3 µg/m³, 3.0× its usual 15.7 Fresno, 15 January: 44.1 µg/m³, 2.9× its usual 15.1 Fresno, 16 January: 37.0 µg/m³, 2.6× its usual 14.1 Fresno, 17 January: 27.2 µg/m³ Fresno, 18 January: 21.0 µg/m³ Fresno, 19 January: 14.5 µg/m³ Fresno, 20 January: 11.9 µg/m³ Manteca Manteca, 10 January: 16.0 µg/m³ Manteca, 11 January: 16.8 µg/m³ Manteca, 12 January: 18.6 µg/m³ Manteca, 13 January: 28.9 µg/m³, 3.1× its usual 9.3 Manteca, 14 January: 28.9 µg/m³, 3.2× its usual 9.0 Manteca, 15 January: 27.2 µg/m³, 3.0× its usual 9.0 Manteca, 16 January: 24.8 µg/m³ Manteca, 17 January: 20.1 µg/m³ Manteca, 18 January: 18.5 µg/m³ Manteca, 19 January: 11.1 µg/m³ Manteca, 20 January: 11.9 µg/m³ Stockton Stockton, 10 January: 14.9 µg/m³ Stockton, 11 January: 25.1 µg/m³ Stockton, 12 January: 19.6 µg/m³ Stockton, 13 January: 28.1 µg/m³, 2.3× its usual 12.3 Stockton, 14 January: 29.8 µg/m³, 2.5× its usual 12.1 Stockton, 15 January: 30.3 µg/m³, 2.5× its usual 12.0 Stockton, 16 January: 30.4 µg/m³, 2.6× its usual 11.8 Stockton, 17 January: 27.8 µg/m³, 2.4× its usual 11.7 Stockton, 18 January: 24.1 µg/m³ Stockton, 19 January: 11.7 µg/m³ Stockton, 20 January: 12.8 µg/m³ Sacramento Sacramento, 10 January: 13.5 µg/m³ Sacramento, 11 January: 23.3 µg/m³ Sacramento, 12 January: 20.4 µg/m³ Sacramento, 13 January: 27.6 µg/m³, 3.4× its usual 8.2 Sacramento, 14 January: 29.9 µg/m³, 3.8× its usual 7.9 Sacramento, 15 January: 27.6 µg/m³, 3.5× its usual 7.9 Sacramento, 16 January: 30.7 µg/m³, 4.0× its usual 7.6 Sacramento, 17 January: 25.2 µg/m³, 3.3× its usual 7.6 Sacramento, 18 January: 22.1 µg/m³ Sacramento, 19 January: 16.4 µg/m³ Sacramento, 20 January: 9.9 µg/m³ Arden-Arcade Arden-Arcade, 10 January: no reading Arden-Arcade, 11 January: no reading Arden-Arcade, 12 January: 22.5 µg/m³ Arden-Arcade, 13 January: 27.3 µg/m³, 3.3× its usual 8.4 Arden-Arcade, 14 January: 29.1 µg/m³, 3.5× its usual 8.3 Arden-Arcade, 15 January: 27.2 µg/m³, 3.4× its usual 8.1 Arden-Arcade, 16 January: 24.3 µg/m³ Arden-Arcade, 17 January: 28.6 µg/m³, 3.6× its usual 8.0 Arden-Arcade, 18 January: 23.1 µg/m³ Arden-Arcade, 19 January: 14.3 µg/m³ Arden-Arcade, 20 January: 13.1 µg/m³ Porterville Porterville, 10 January: 9.2 µg/m³ Porterville, 11 January: 15.4 µg/m³ Porterville, 12 January: 18.6 µg/m³ Porterville, 13 January: 26.1 µg/m³, 2.7× its usual 9.8 Porterville, 14 January: 31.9 µg/m³, 3.3× its usual 9.8 Porterville, 15 January: 30.0 µg/m³, 3.1× its usual 9.6 Porterville, 16 January: 28.2 µg/m³, 3.0× its usual 9.5 Porterville, 17 January: 22.3 µg/m³ Porterville, 18 January: 17.9 µg/m³ Porterville, 19 January: 12.5 µg/m³ Porterville, 20 January: 9.0 µg/m³ Corcoran Corcoran, 10 January: 15.8 µg/m³ Corcoran, 11 January: 19.9 µg/m³ Corcoran, 12 January: 26.2 µg/m³ Corcoran, 13 January: 24.0 µg/m³ Corcoran, 14 January: 34.0 µg/m³, 2.8× its usual 12.1 Corcoran, 15 January: 31.6 µg/m³, 2.6× its usual 12.1 Corcoran, 16 January: 25.4 µg/m³, 2.1× its usual 12.1 Corcoran, 17 January: 22.1 µg/m³ Corcoran, 18 January: 16.4 µg/m³ Corcoran, 19 January: 13.0 µg/m³ Corcoran, 20 January: 16.5 µg/m³ Hanford Hanford, 10 January: no reading Hanford, 11 January: no reading Hanford, 12 January: no reading Hanford, 13 January: 27.0 µg/m³ Hanford, 14 January: 33.7 µg/m³, 2.3× its usual 14.4 Hanford, 15 January: 39.2 µg/m³, 2.8× its usual 14.0 Hanford, 16 January: 32.0 µg/m³, 2.3× its usual 14.0 Hanford, 17 January: 24.1 µg/m³ Hanford, 18 January: 15.3 µg/m³ Hanford, 19 January: 13.8 µg/m³ Hanford, 20 January: 11.1 µg/m³ Clovis Clovis, 10 January: 9.6 µg/m³ Clovis, 11 January: 13.9 µg/m³ Clovis, 12 January: 14.0 µg/m³ Clovis, 13 January: 18.1 µg/m³ Clovis, 14 January: 31.7 µg/m³, 2.7× its usual 11.7 Clovis, 15 January: 31.0 µg/m³, 2.8× its usual 11.1 Clovis, 16 January: 27.6 µg/m³, 2.8× its usual 10.0 Clovis, 17 January: 19.5 µg/m³ Clovis, 18 January: 14.9 µg/m³ Clovis, 19 January: 9.5 µg/m³ Clovis, 20 January: 6.6 µg/m³ Medford Medford, 10 January: 19.1 µg/m³ Medford, 11 January: 19.9 µg/m³ Medford, 12 January: 23.2 µg/m³ Medford, 13 January: 27.4 µg/m³ Medford, 14 January: 25.9 µg/m³, 2.6× its usual 9.8 Medford, 15 January: 21.9 µg/m³ Medford, 16 January: 24.6 µg/m³ Medford, 17 January: 25.6 µg/m³ Medford, 18 January: 24.2 µg/m³ Medford, 19 January: 20.6 µg/m³ Medford, 20 January: 21.4 µg/m³ Yuba City Yuba City, 10 January: 18.9 µg/m³ Yuba City, 11 January: 23.5 µg/m³ Yuba City, 12 January: 20.4 µg/m³ Yuba City, 13 January: 23.0 µg/m³ Yuba City, 14 January: 25.7 µg/m³, 4.0× its usual 6.4 Yuba City, 15 January: 22.8 µg/m³ Yuba City, 16 January: 24.1 µg/m³ Yuba City, 17 January: 24.1 µg/m³ Yuba City, 18 January: 17.4 µg/m³ Yuba City, 19 January: 17.5 µg/m³ Yuba City, 20 January: 9.0 µg/m³ Chico Chico, 10 January: 2.4 µg/m³ Chico, 11 January: 4.7 µg/m³ Chico, 12 January: 2.5 µg/m³ Chico, 13 January: 23.9 µg/m³ Chico, 14 January: 25.0 µg/m³, 3.2× its usual 7.7 Chico, 15 January: 17.4 µg/m³ Chico, 16 January: 18.7 µg/m³ Chico, 17 January: 21.4 µg/m³ Chico, 18 January: 20.0 µg/m³ Chico, 19 January: 21.2 µg/m³ Chico, 20 January: 14.5 µg/m³ South San Francisco South San Francisco, 10 January: 9.5 µg/m³ South San Francisco, 11 January: 10.3 µg/m³ South San Francisco, 12 January: 12.1 µg/m³ South San Francisco, 13 January: 18.7 µg/m³ South San Francisco, 14 January: 21.7 µg/m³ South San Francisco, 15 January: 27.6 µg/m³, 3.9× its usual 7.0 South San Francisco, 16 January: 13.7 µg/m³ South San Francisco, 17 January: 18.1 µg/m³ South San Francisco, 18 January: 22.0 µg/m³ South San Francisco, 19 January: 17.9 µg/m³ South San Francisco, 20 January: 15.3 µg/m³ Merced Merced, 10 January: 15.2 µg/m³ Merced, 11 January: 13.6 µg/m³ Merced, 12 January: 15.2 µg/m³ Merced, 13 January: 18.3 µg/m³ Merced, 14 January: 21.4 µg/m³ Merced, 15 January: 26.8 µg/m³, 2.5× its usual 10.7 Merced, 16 January: 24.0 µg/m³ Merced, 17 January: 19.3 µg/m³ Merced, 18 January: 15.5 µg/m³ Merced, 19 January: 13.8 µg/m³ Merced, 20 January: 13.7 µg/m³ Madera Madera, 10 January: 12.9 µg/m³ Madera, 11 January: 13.9 µg/m³ Madera, 12 January: 13.9 µg/m³ Madera, 13 January: 20.1 µg/m³ Madera, 14 January: 23.8 µg/m³ Madera, 15 January: 26.2 µg/m³, 2.6× its usual 10.0 Madera, 16 January: 31.2 µg/m³, 3.3× its usual 9.6 Madera, 17 January: 26.2 µg/m³, 2.8× its usual 9.3 Madera, 18 January: 18.6 µg/m³ Madera, 19 January: 15.4 µg/m³ Madera, 20 January: 12.3 µg/m³ Fremont Fremont, 10 January: 8.5 µg/m³ Fremont, 11 January: 9.9 µg/m³ Fremont, 12 January: 13.7 µg/m³ Fremont, 13 January: 16.8 µg/m³ Fremont, 14 January: 12.2 µg/m³ Fremont, 15 January: 25.2 µg/m³, 2.3× its usual 11.1 Fremont, 16 January: 16.1 µg/m³ Fremont, 17 January: 19.5 µg/m³ Fremont, 18 January: 19.6 µg/m³ Fremont, 19 January: 9.9 µg/m³ Fremont, 20 January: 11.7 µg/m³ Vallejo Vallejo, 10 January: 8.5 µg/m³ Vallejo, 11 January: 13.0 µg/m³ Vallejo, 12 January: 15.6 µg/m³ Vallejo, 13 January: 19.6 µg/m³ Vallejo, 14 January: 23.1 µg/m³ Vallejo, 15 January: 25.1 µg/m³, 2.8× its usual 9.1 Vallejo, 16 January: 20.8 µg/m³ Vallejo, 17 January: 21.9 µg/m³ Vallejo, 18 January: 19.8 µg/m³ Vallejo, 19 January: 15.2 µg/m³ Vallejo, 20 January: 8.3 µg/m³ Oakland Oakland, 10 January: 12.5 µg/m³ Oakland, 11 January: 15.7 µg/m³ Oakland, 12 January: 12.9 µg/m³ Oakland, 13 January: 19.3 µg/m³ Oakland, 14 January: 22.6 µg/m³ Oakland, 15 January: 25.0 µg/m³, 3.6× its usual 7.0 Oakland, 16 January: 16.9 µg/m³ Oakland, 17 January: 19.1 µg/m³ Oakland, 18 January: 22.5 µg/m³ Oakland, 19 January: 15.5 µg/m³ Oakland, 20 January: 13.8 µg/m³ Woodland Woodland, 10 January: 19.3 µg/m³ Woodland, 11 January: 18.7 µg/m³ Woodland, 12 January: 26.8 µg/m³ Woodland, 13 January: 20.3 µg/m³ Woodland, 14 January: 24.5 µg/m³ Woodland, 15 January: 21.9 µg/m³ Woodland, 16 January: 26.8 µg/m³, 3.7× its usual 7.2 Woodland, 17 January: 24.9 µg/m³ Woodland, 18 January: 18.7 µg/m³ Woodland, 19 January: 15.2 µg/m³ Woodland, 20 January: 12.1 µg/m³ Florin Florin, 10 January: 15.6 µg/m³ Florin, 11 January: 24.0 µg/m³ Florin, 12 January: 20.2 µg/m³ Florin, 13 January: 27.3 µg/m³ Florin, 14 January: 31.6 µg/m³ Florin, 15 January: 32.0 µg/m³ Florin, 16 January: 32.3 µg/m³ Florin, 17 January: 34.7 µg/m³, 2.1× its usual 16.7 Florin, 18 January: 31.2 µg/m³ Florin, 19 January: 25.6 µg/m³ Florin, 20 January: 17.2 µg/m³ 10 Jan 12 14 16 18 20 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. Good 0–50
Moderate 51–100
Sensitive groups 101–150
Unhealthy 151–200
Very unhealthy 201–300
Hazardous 301+
Every city it reached
City Days Highest Usual Above usual
Sacramento California, United States 5 16 January 7.6 4.0× Yuba City California, United States 1 14 January 6.4 4.0× South San Francisco California, United States 1 15 January 7.0 3.9× Woodland California, United States 1 16 January 7.2 3.7× Oakland California, United States 1 15 January 7.0 3.6× Arden-Arcade California, United States 4 14 January 8.3 3.5× Modesto California, United States 5 16 January 11.1 3.3× Porterville California, United States 4 14 January 9.8 3.3× Madera California, United States 3 16 January 9.6 3.3× Chico California, United States 1 14 January 7.7 3.2× Manteca California, United States 3 13 January 9.3 3.1× Fresno California, United States 4 14 January 15.7 3.0× Bakersfield California, United States 5 14 January 13.6 3.0× Hanford California, United States 3 15 January 14.0 2.8× Corcoran California, United States 3 14 January 12.1 2.8× Vallejo California, United States 1 15 January 9.1 2.8× Clovis California, United States 3 14 January 11.7 2.7× Visalia California, United States 4 14 January 14.2 2.6× Stockton California, United States 5 16 January 11.8 2.6× Medford Oregon, United States 1 14 January 9.8 2.6× Merced California, United States 1 15 January 10.7 2.5× Fremont California, United States 1 15 January 11.1 2.3× Florin California, United States 1 17 January 16.7 2.1×
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 46 of 130 episodes in the United States since our records began, by cities reached.
Eastern United States and Canada, 25 June to 2 July 2023 280 North-eastern United States and Canada, July 2026 264 Eastern United States and Canada, May and June 2023 261 North-eastern United States and Canada, 30 July to 9 August 2025 241 Eastern United States and Canada, July 2023 240 North-eastern United States and Canada, 3 to 9 June 2025 196 Eastern United States and Canada, 14 to 19 June 2023 161 North-eastern United States and Canada, 12 to 16 July 2025 119 North-western United States and Canada, August 2023 110 North-eastern United States and Canada, 10 to 14 June 2025 104 North-western United States and Canada, 4 to 11 August 2026 99 North-eastern United States and Canada, 14 to 19 February 2026 96 California and Oregon, United States, January 2026 23 Bars: cities reached; colour: the level of the episode's highest daily reading. All 130 .
Use this page SmogRank, California and Oregon, United States, January 2026: 23 cities with PM2.5 at twice their usual or more, 13 to 17 January 2026, smogrank.com/episodes/2026-01-california-and-oregon-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.
