SmogRank / World / North America / United States / California

Most polluted cities in California, United States

123 measured cities, last 30 days; 0 above the WHO 24-hour guideline. Worst: Hanford at 13.7 µg/m³, #390 in the world.

About 0 people in these 22 cities breathed unhealthy air on an average day over the last 30 days.

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.

Idaho: 12 measured citiesArizona: 16 measured citiesCalifornia: 123 measured citiesOregon: 43 measured citiesUtah: 20 measured citiesNevada: 11 measured cities#123 Big Bear City: 3.0 µg/m³#122 Lompoc: 3.6 µg/m³#121 Vacaville: 3.7 µg/m³#120 Yreka: 3.8 µg/m³#119 Sunnyvale: 4.2 µg/m³#117 Atascadero: 4.5 µg/m³#118 Ridgecrest: 4.5 µg/m³#116 Lancaster: 4.6 µg/m³#115 Ceres: 4.7 µg/m³#111 Folsom: 4.8 µg/m³#112 Hollister: 4.8 µg/m³#113 Indio: 4.8 µg/m³#114 Sebastopol: 4.8 µg/m³#110 Palo Alto: 4.9 µg/m³#109 North Auburn: 5.0 µg/m³#108 Fremont: 5.1 µg/m³#106 Ojai: 5.2 µg/m³#107 Windsor: 5.2 µg/m³#104 Truckee: 5.3 µg/m³#105 Red Bluff: 5.3 µg/m³#103 San Rafael: 5.5 µg/m³#100 Chico: 5.6 µg/m³#101 Crestline: 5.6 µg/m³#102 Paradise: 5.6 µg/m³#98 Rancho Murieta: 5.7 µg/m³#99 Solvang: 5.7 µg/m³#96 Los Banos: 5.8 µg/m³#97 Ukiah: 5.8 µg/m³#94 Seaside: 5.9 µg/m³#95 Tracy: 5.9 µg/m³#92 El Centro: 6.0 µg/m³#93 South San Francisco: 6.0 µg/m³#91 Goleta: 6.1 µg/m³#90 Redding: 6.2 µg/m³#87 Brawley: 6.3 µg/m³#88 Gilroy: 6.3 µg/m³#89 Oakland: 6.3 µg/m³#86 Alpine: 6.4 µg/m³#84 Fillmore: 6.5 µg/m³#85 El Rio: 6.5 µg/m³#83 Santa Cruz: 6.6 µg/m³#79 Concord: 6.7 µg/m³#80 Roseville: 6.7 µg/m³#81 Simi Valley: 6.7 µg/m³#82 Temecula: 6.7 µg/m³#75 Banning: 6.8 µg/m³#76 Guadalupe: 6.8 µg/m³#77 Huron: 6.8 µg/m³#78 King City: 6.8 µg/m³#70 Berkeley: 6.9 µg/m³#71 Florin: 6.9 µg/m³#72 Lincoln: 6.9 µg/m³#73 Morro Bay: 6.9 µg/m³#74 Sacramento: 6.9 µg/m³#68 Calexico: 7.0 µg/m³#69 La Crescenta-Montrose: 7.0 µg/m³#67 Alta Sierra: 7.1 µg/m³#64 Delano: 7.2 µg/m³#65 San Francisco: 7.2 µg/m³#66 Stockton: 7.2 µg/m³#57 Galt: 7.3 µg/m³#58 Modesto: 7.3 µg/m³#59 Prunedale: 7.3 µg/m³#60 South Lake Tahoe: 7.3 µg/m³#61 Thousand Oaks: 7.3 µg/m³#62 Vallejo: 7.3 µg/m³#63 Victorville: 7.3 µg/m³#56 Davis: 7.4 µg/m³#53 Carpinteria: 7.6 µg/m³#54 Livermore: 7.6 µg/m³#55 Salinas: 7.6 µg/m³#48 Elk Grove: 7.8 µg/m³#49 Gridley: 7.8 µg/m³#50 Redwood City: 7.8 µg/m³#51 Torrance: 7.8 µg/m³#52 Arden-Arcade: 7.8 µg/m³#47 Willows: 7.9 µg/m³#46 Orcutt: 8.1 µg/m³#44 Colusa: 8.2 µg/m³#45 Lomita: 8.2 µg/m³#43 Poway: 8.3 µg/m³#42 San Leandro: 8.4 µg/m³#39 Agoura: 8.5 µg/m³#40 El Cajon: 8.5 µg/m³#41 Yuba City: 8.5 µg/m³#38 Santa Clarita: 8.6 µg/m³#34 Anaheim: 8.7 µg/m³#35 Ben Lomond: 8.7 µg/m³#36 Burbank: 8.7 µg/m³#37 Oceano: 8.7 µg/m³#32 Lake Elsinore: 8.8 µg/m³#33 Santa Monica: 8.8 µg/m³#31 Long Beach: 8.9 µg/m³#30 Manteca: 9.0 µg/m³#29 Glendora: 9.1 µg/m³#28 Porterville: 9.2 µg/m³#27 Inglewood: 9.3 µg/m³#24 Carson: 9.4 µg/m³#25 San Jose: 9.4 µg/m³#26 Turlock: 9.4 µg/m³#23 Mission Viejo: 9.5 µg/m³#22 Chula Vista: 9.7 µg/m³#21 Bakersfield: 9.8 µg/m³#19 Hawthorne: 10.0 µg/m³#20 Merced: 10.0 µg/m³#18 San Diego: 10.1 µg/m³#16 Compton: 10.5 µg/m³#17 Tulare: 10.5 µg/m³#14 Madera: 10.6 µg/m³#15 Richmond: 10.6 µg/m³#13 Cambria: 10.8 µg/m³#12 Los Angeles: 10.9 µg/m³#11 Whittier: 11.0 µg/m³#10 Fontana: 11.3 µg/m³#9 Oceanside: 12.2 µg/m³#7 Clovis: 12.4 µg/m³#8 Fresno: 12.4 µg/m³#6 Riverside: 12.6 µg/m³#5 Corcoran: 12.8 µg/m³#4 Imperial Beach: 13.1 µg/m³#2 Mecca: 13.6 µg/m³#3 Jurupa Valley: 13.6 µg/m³#1 Hanford: 13.7 µg/m³
Each dot is a measured city, coloured by its PM2.5; tap a dot to open the city.
← Fresno 0 0.750
Every measured city in California, United States with monitors in two or more places, one column each, ranked by people breathing unhealthy air: height is people on an average day, colour its average. Point at it to read a city; tap to open it.
  1. 1Fresno 0
  2. 2Los Angeles 0
  3. 3Compton 0
  4. 4Merced 0
  5. 5Bakersfield 0
  6. 6Carsonlow-cost sensors 0
  7. 6San Jose 0
  8. 8Inglewoodlow-cost sensors 0
  9. 9Santa Monicalow-cost sensors 0
  10. 10Agouralow-cost sensors 0
  11. 11Elk Grovelow-cost sensors 0
  12. 11Torrancelow-cost sensors 0
  13. 13Prunedalelow-cost sensors 0
  14. 14La Crescenta-Montroselow-cost sensorslast full day 3 Oct 0
  15. 15Banning 0
  16. 16Goletalow-cost sensors 0
  17. 17Seasidelow-cost sensors 0
  18. 18Windsorlow-cost sensors 0
  19. 19Fremontlow-cost sensors 0
  20. 20Palo Altolow-cost sensors 0
  21. 21Cereslow-cost sensors 0
  22. 22Sunnyvalelow-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.

Good0–50
Moderate51–100
Sensitive groups101–150
Unhealthy151–200
Very unhealthy201–300
Hazardous301+

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

Estimated: cities without a monitor

California cities we can't measure, with model estimates for the last 7 days. Listed by population, not ranked: estimates aren't precise enough to rank. Model estimates from the Copernicus Atmosphere Monitoring Service (CAMS), adjusted to measured cities nearby where there are any. Adjusted, a single day lands within ×1.5 of what a monitor would read about two times in three; unadjusted, it can be off by half or double. Treat them as a guide, not a measurement.

City7-day estimateBand
Santa Ana≈ 9 µg/m³Good
Irvine≈ 9 µg/m³Good
San Bernardino≈ 7 µg/m³Good
Oxnard≈ 6 µg/m³Good
Moreno Valley≈ 7 µg/m³Good
Huntington Beach≈ 9 µg/m³Good
Glendale≈ 13 µg/m³Moderate
Garden Grove≈ 8 µg/m³Good
Rancho Cucamonga≈ 10 µg/m³Moderate
Corona≈ 10 µg/m³Moderate
Palmdale≈ 6 µg/m³Good
Hayward≈ 10 µg/m³Moderate
Pomona≈ 9 µg/m³Good
Escondido≈ 10 µg/m³Moderate
Valencia≈ 6 µg/m³Good
Pasadena≈ 11 µg/m³Moderate
Orange≈ 9 µg/m³Good
Fullerton≈ 11 µg/m³Moderate
East Los Angeles≈ 11 µg/m³Moderate
Santa Clara≈ 10 µg/m³Moderate
El Monte≈ 11 µg/m³Moderate
Carlsbad≈ 10 µg/m³Moderate
Downey≈ 11 µg/m³Moderate
Costa Mesa≈ 9 µg/m³Good
Fairfield≈ 5 µg/m³Good
Antioch≈ 10 µg/m³Moderate
Murrieta≈ 9 µg/m³Good
West Covina≈ 11 µg/m³Moderate
Norwalk≈ 11 µg/m³Moderate
Daly City≈ 7 µg/m³Good
Santa Maria≈ 8 µg/m³Good
Rialto≈ 7 µg/m³Good
Vista≈ 10 µg/m³Moderate
Ventura≈ 5 µg/m³Good
South Gate≈ 13 µg/m³Moderate
Hesperia≈ 4 µg/m³Good
San Marcos≈ 10 µg/m³Moderate
Westminster≈ 8 µg/m³Good
Santa Barbara≈ 5 µg/m³Good
Menifee≈ 9 µg/m³Good

Bad-air episodes in California

Times when many cities around here had PM2.5 at twice their usual or more on the same days.

Use this board

SmogRank, most polluted cities in California, United States, PM2.5, last 30 days to 6 Oct 2026, 22:00 UTC, smogrank.com/us/region/california?w=30d.

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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.

Updated 2026-10-06 22:07 UTC. Values are PM2.5 (fine particles), the median of each city's monitors, as the US AQI PM2.5 sub-index.