SmogRank / World / North America / United States / California

Most polluted cities in California, United States

112 measured cities, this year; 100 above the WHO annual guideline. Worst: Jurupa Valley at 14.1 µg/m³, #608 in the world.

About 26.3K people in these 14 cities breathed unhealthy air on an average day so far this year.

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: 10 measured citiesArizona: 16 measured citiesCalifornia: 112 measured citiesOregon: 43 measured citiesUtah: 21 measured citiesNevada: 11 measured cities#112 San Mateo: 3.3 µg/m³#111 Lompoc: 3.4 µg/m³#110 Sunnyvale: 3.9 µg/m³#109 Palo Alto: 4.5 µg/m³#106 Hollister: 4.7 µg/m³#107 Los Banos: 4.7 µg/m³#108 Ridgecrest: 4.7 µg/m³#103 Folsom: 4.8 µg/m³#104 Truckee: 4.8 µg/m³#105 Vacaville: 4.8 µg/m³#102 Solvang: 4.9 µg/m³#101 Paradise: 5.0 µg/m³#99 Lancaster: 5.1 µg/m³#100 San Rafael: 5.1 µg/m³#98 Big Bear City: 5.2 µg/m³#94 Goleta: 5.4 µg/m³#95 Tracy: 5.4 µg/m³#96 Willows: 5.4 µg/m³#97 Red Bluff: 5.4 µg/m³#93 Crescent City: 5.5 µg/m³#90 Chico: 5.7 µg/m³#91 Concord: 5.7 µg/m³#92 Crestline: 5.7 µg/m³#86 Ojai: 5.8 µg/m³#87 Sebastopol: 5.8 µg/m³#88 Thousand Oaks: 5.8 µg/m³#89 Redding: 5.8 µg/m³#82 Atascadero: 5.9 µg/m³#83 Fremont: 5.9 µg/m³#84 Gilroy: 5.9 µg/m³#85 North Auburn: 5.9 µg/m³#81 Yreka: 6.0 µg/m³#78 El Rio: 6.1 µg/m³#79 Rancho Murieta: 6.1 µg/m³#80 Ukiah: 6.1 µg/m³#77 Redwood City: 6.2 µg/m³#74 Alpine: 6.3 µg/m³#75 Colusa: 6.3 µg/m³#76 Orcutt: 6.3 µg/m³#70 Fillmore: 6.5 µg/m³#71 Huron: 6.5 µg/m³#72 Lincoln: 6.5 µg/m³#73 Temecula: 6.5 µg/m³#68 Galt: 6.6 µg/m³#69 Santa Cruz: 6.6 µg/m³#65 Banning: 6.7 µg/m³#66 Ben Lomond: 6.7 µg/m³#67 Brawley: 6.7 µg/m³#63 El Centro: 6.8 µg/m³#64 Livermore: 6.8 µg/m³#56 Carpinteria: 6.9 µg/m³#57 Davis: 6.9 µg/m³#58 Guadalupe: 6.9 µg/m³#59 Oceano: 6.9 µg/m³#60 Roseville: 6.9 µg/m³#61 Sacramento: 6.9 µg/m³#62 Vallejo: 6.9 µg/m³#53 Berkeley: 7.1 µg/m³#54 King City: 7.1 µg/m³#55 Salinas: 7.1 µg/m³#52 Gridley: 7.2 µg/m³#50 Indio: 7.3 µg/m³#51 San Leandro: 7.3 µg/m³#48 San Francisco: 7.4 µg/m³#49 Arden-Arcade: 7.4 µg/m³#47 Simi Valley: 7.5 µg/m³#46 Yuba City: 7.7 µg/m³#44 Victorville: 7.8 µg/m³#45 Woodland: 7.8 µg/m³#43 Oakland: 7.9 µg/m³#41 Poway: 8.0 µg/m³#42 Stockton: 8.0 µg/m³#38 Manteca: 8.1 µg/m³#39 Modesto: 8.1 µg/m³#40 San Luis Obispo: 8.1 µg/m³#37 Alta Sierra: 8.2 µg/m³#35 Santa Clarita: 8.3 µg/m³#36 Turlock: 8.3 µg/m³#34 San Jose: 8.4 µg/m³#30 El Cajon: 8.6 µg/m³#31 Oceanside: 8.6 µg/m³#32 Richmond: 8.6 µg/m³#33 Torrance: 8.6 µg/m³#29 Lake Elsinore: 8.7 µg/m³#27 Chula Vista: 8.9 µg/m³#28 Mission Viejo: 8.9 µg/m³#25 Burbank: 9.2 µg/m³#26 Glendora: 9.2 µg/m³#24 Merced: 9.3 µg/m³#23 Long Beach: 9.4 µg/m³#22 Madera: 9.5 µg/m³#20 Calexico: 9.6 µg/m³#21 San Diego: 9.6 µg/m³#18 Clovis: 9.8 µg/m³#19 Santa Monica: 9.8 µg/m³#17 Porterville: 9.9 µg/m³#16 Anaheim: 10.1 µg/m³#15 South Lake Tahoe: 10.7 µg/m³#14 Hanford: 10.9 µg/m³#12 Compton: 11.1 µg/m³#13 Fresno: 11.1 µg/m³#11 Los Angeles: 11.2 µg/m³#9 Corcoran: 11.5 µg/m³#10 Fontana: 11.5 µg/m³#8 Bakersfield: 11.9 µg/m³#6 Delano: 12.2 µg/m³#7 Visalia: 12.2 µg/m³#5 Tulare: 12.3 µg/m³#4 Whittier: 12.4 µg/m³#3 Riverside: 12.6 µg/m³#2 Imperial Beach: 12.7 µg/m³#1 Jurupa Valley: 14.1 µg/m³
Each dot is a measured city, coloured by its PM2.5; tap a dot to open the city.
← Bakersfield 12.1K 10K0
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. 1Bakersfield 12.1K
  2. 2Fresno 11.7K
  3. 3Fremontlow-cost sensors 1.73K
  4. 4Torrancelow-cost sensors 530
  5. 5Palo Altolow-cost sensors 240
  6. 6Los Angeles 0
  7. 7Compton 0
  8. 8Santa Monicalow-cost sensors 0
  9. 9Merced 0
  10. 10San Jose 0
  11. 11Banning 0
  12. 12Goletalow-cost sensors 0
  13. 13Sunnyvalelow-cost sensors 0
  14. 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.

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, this year to 6 Oct 2026, 22:00 UTC, smogrank.com/us/region/california?w=year.

Download top 10 (PNG)

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.