SmogRank / World / United States / California / 2026
Most polluted cities in California, United States, 2026
114 cities in California, United States ranked by their average PM2.5 so far (278 of 365 days); 102 above the WHO annual guideline (5.0 µg/m³). Worst: Jurupa Valley at 14.1 µg/m³, #609 of 2,745 cities in the world. Cleanest: San Mateo at 3.3. A city needs measurements on 70% of the days to be ranked.
About 26.3K people in these 14 cities breathed unhealthy air on an average day of 2026.
Ranked by people: each city's population times its share of unhealthy days, those with a daily mean over 35.4 µg/m³ (US AQI 101+). That is how many people living there breathed unhealthy air on an average day. Only cities measured at 2 or more places at least 3 km apart are ranked: one monitor shouldn't speak for a whole city. Population is the city itself, not its wider metro area.
- 1Bakersfield 12.1K
- 2Fresno 11.7K
- 3Fremontlow-cost sensors 1.73K
- 4Torrancelow-cost sensors 530
- 5Palo Altolow-cost sensors 240
- 6Los Angeles 0
- 7Compton 0
- 8Santa Monicalow-cost sensors 0
- 9Merced 0
- 10San Jose 0
- 11Banning 0
- 12Goletalow-cost sensors 0
- 13Sunnyvalelow-cost sensors 0
- 14San Mateolow-cost sensors 0
Low-cost sensors: consumer units, counted only in cities with no government-grade monitor; they read close to reference monitors on the whole, but 15 to 25% high in humid air. How we use them.
The US EPA's Air Quality Index for PM2.5 (2024 breakpoints). Show values as: µg/m³ · US AQI · India AQI · China AQI · European AQI · UK DAQI · Canada AQHI+. About the scales
All cities in the world, 2026 · All cities in United States, 2026 · California now
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SmogRank, most polluted cities in California, United States, PM2.5, 2026 (so far), smogrank.com/us/region/california/history/2026 (accessed 6 Oct 2026).
You're welcome to reuse a single chart, image or figure with this citation and a link. Terms. Raw monitor readings in bulk are published by OpenAQ, under each provider's licence.