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AirHistory

Air Quality in California

10-year air quality trends for 53 monitored areas in California.

See full California air quality rankings →
53
Cities
49
Avg AQI (5yr)
38
Improving
6
Stable
9
Worsening

All Monitored Areas in California

Humboldt, California

Humboldt County · AQI 28 (5yr avg) · Improving · Ozone

A

Napa, California

Napa County · AQI 39 (5yr avg) · Improving · PM2.5

B

Marin, California

Marin County · AQI 36 (5yr avg) · Improving · PM2.5

B

Lake, California

Lake County · AQI 32 (5yr avg) · Improving · Ozone

B

San Mateo, California

San Mateo County · AQI 36 (5yr avg) · Improving · PM2.5

B

Amador, California

Amador County · AQI 37 (5yr avg) · Improving · Ozone

B

Sonoma, California

Sonoma County · AQI 36 (5yr avg) · Improving · Ozone

B

San Francisco, California

San Francisco County · AQI 38 (5yr avg) · Improving · PM2.5

B

Solano, California

Solano County · AQI 45 (5yr avg) · Improving · PM2.5

B

Calaveras, California

Calaveras County · AQI 44 (5yr avg) · Improving · Ozone

B

Tuolumne, California

Tuolumne County · AQI 41 (5yr avg) · Improving · Ozone

B

Santa Barbara, California

Santa Barbara County · AQI 46 (5yr avg) · Improving · PM2.5

B

Santa Cruz, California

Santa Cruz County · AQI 37 (5yr avg) · Stable · PM2.5

B

Yolo, California

Yolo County · AQI 43 (5yr avg) · Improving · Ozone

B

Glenn, California

Glenn County · AQI 43 (5yr avg) · Improving · Ozone

C

Monterey, California

Monterey County · AQI 40 (5yr avg) · Stable · Ozone

C

San Benito, California

San Benito County · AQI 41 (5yr avg) · Stable · Ozone

C

San Joaquin, California

San Joaquin County · AQI 50 (5yr avg) · Improving · PM2.5

C

San Luis Obispo, California

San Luis Obispo County · AQI 51 (5yr avg) · Improving · PM2.5

C

Ventura, California

Ventura County · AQI 50 (5yr avg) · Improving · PM2.5

C

Alameda, California

Alameda County · AQI 50 (5yr avg) · Improving · PM2.5

C

Butte, California

Butte County · AQI 52 (5yr avg) · Improving · PM2.5

C

Contra Costa, California

Contra Costa County · AQI 48 (5yr avg) · Stable · PM2.5

C

El Dorado, California

El Dorado County · AQI 43 (5yr avg) · Stable · Ozone

C

Santa Clara, California

Santa Clara County · AQI 49 (5yr avg) · Stable · PM2.5

C

Orange, California

Orange County · AQI 54 (5yr avg) · Improving · PM2.5

C

Colusa, California

Colusa County · AQI 47 (5yr avg) · Stable · PM2.5

C

Madera, California

Madera County · AQI 56 (5yr avg) · Improving · Ozone

C

Merced, California

Merced County · AQI 54 (5yr avg) · Improving · Ozone

C

Shasta, California

Shasta County · AQI 44 (5yr avg) · Stable · Ozone

C

Sutter, California

Sutter County · AQI 52 (5yr avg) · Improving · PM2.5

C

Tehama, California

Tehama County · AQI 45 (5yr avg) · Stable · Ozone

C

Del Norte, California

Del Norte County · AQI 32 (5yr avg) · Worsening · PM2.5

C

Nevada, California

Nevada County · AQI 47 (5yr avg) · Stable · Ozone

C

Sacramento, California

Sacramento County · AQI 53 (5yr avg) · Improving · Ozone

C

Mendocino, California

Mendocino County · AQI 46 (5yr avg) · Worsening · PM2.5

C

Mariposa, California

Mariposa County · AQI 49 (5yr avg) · Improving · Ozone

C

Trinity, California

Trinity County · AQI 32 (5yr avg) · Worsening · PM2.5

C

Siskiyou, California

Siskiyou County · AQI 41 (5yr avg) · Worsening · Ozone

D

Fresno, California

Fresno County · AQI 68 (5yr avg) · Improving · Ozone

D

Stanislaus, California

Stanislaus County · AQI 57 (5yr avg) · Improving · PM2.5

D

Imperial, California

Imperial County · AQI 61 (5yr avg) · Improving · PM2.5

D

Kings, California

Kings County · AQI 64 (5yr avg) · Improving · Ozone

D

Placer, California

Placer County · AQI 54 (5yr avg) · Worsening · Ozone

D

Kern, California

Kern County · AQI 77 (5yr avg) · Improving · Ozone

D

Mono, California

Mono County · AQI 33 (5yr avg) · Worsening · PM2.5

D

Tulare, California

Tulare County · AQI 75 (5yr avg) · Improving · Ozone

D

Plumas, California

Plumas County · AQI 52 (5yr avg) · Worsening · PM2.5

D

Los Angeles, California

Los Angeles County · AQI 75 (5yr avg) · Improving · PM2.5

D

Riverside, California

Riverside County · AQI 82 (5yr avg) · Improving · Ozone

D

San Diego, California

San Diego County · AQI 67 (5yr avg) · Stable · PM2.5

D

San Bernardino, California

San Bernardino County · AQI 82 (5yr avg) · Improving · Ozone

F

Inyo, California

Inyo County · AQI 57 (5yr avg) · Worsening · Ozone

F
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Frequently Asked Questions

California has 53 monitored areas with an average 5-year AQI of 49 and an average Air Quality Grade of C. 38 cities are improving, 9 are worsening, and 6 are stable.

Humboldt, California has the best Air Quality Grade (A) in California with a 5-year average AQI of 28.

Of 53 monitored areas in California, 38 are showing improving trends, 9 are worsening, and 6 remain stable over the past decade.

Sources: EPA Air Quality System (AQS)
Last updated: