Air Quality Forecast

Legend

Tuesday, April 11

Forecast Reporting Zones

Northern Zone

American Canyon

Angwin

Bel Marin Keys

Boyes Hot Springs

Calistoga

Cotati

Deer Park

El Verano

Eldridge

Fairfax

Forest Knolls

Fulton

Glen Ellen

Graton

Greenbrae

Hamilton AFB

Kentfield

Kenwood

Lagunitas

Marinwood

Napa

Nicasio

Novato

Oakville

Penngrove

Petaluma

Pope Valley

Rohnert Park

Ross

Rutherford

San Anselmo

San Geronimo

San Rafael

Santa Rosa

Sebastopol

Sonoma

St. Helena

Vallejo

Valley Ford

Vineburg

Windsor

Woodacre

Yountville

Coast and Central Bay

Alameda

Albany

Belmont

Belvedere

Berkeley

Bolinas

Brisbane

Burlingame

Colma

Corte Madera

Crockett

Daly City

Dillon Beach

El Cerrito

El Granada

El Sobrante

Emeryville

Foster City

Half Moon Bay

Hercules

Hillsborough

Inverness

Kensington

La Honda

Larkspur

Marin City

Marshall

Mill Valley

Millbrae

Montara

Moss Beach

Oakland

Olema

Pacifica

Pescadero

Piedmont

Pinole

Point Reyes Stn.

Point Richmond

Richmond

Rodeo

San Bruno

San Carlos

San Francisco

San Gregorio

San Mateo

San Pablo

San Quentin

Sausalito

South S.F.

Stinson Beach

Tamalpais Vly

Tiburon

Tomales

Eastern Zone

Alamo

Antioch

Benicia

Bethel Island

Birds Landing

Brentwood

Byron

Clayton

Concord

Cordelia

Danville

Diablo

Discovery Bay

Dublin

Fairfield

Lafayette

Livermore

Martinez

Moraga

Oakley

Orinda

Pittsburg

Pleasant Hill

Pleasanton

Port Costa

Rheem Valley

San Ramon

Suisun City

Sunol

Travis AFB

Walnut Creek

South Central Bay

Atherton

Castro Valley

East Palo Alto

Fremont

Hayward

Los Altos

Los Altos Hills

Menlo Park

Mountain View

Newark

Palo Alto

Portola Valley

Redwood City

San Leandro

San Lorenzo

Union City

Woodside

Santa Clara Valley

Alum Rock

Alviso

Campbell

Coyote

Cupertino

Gilroy

Los Gatos

Milpitas

Morgan Hill

New Almaden

Redwood Estates

San Jose

San Martin

Santa Clara

Saratoga

Sunnyvale

Mon

Tue

Wed

Thu

Fri

Northern Zone

OZONE

Coast and Central Bay

OZONE

Eastern Zone

OZONE

South Central Bay

OZONE

Santa Clara Valley

OZONE

Forecast-Map-Legend-Title

Good-Range

Good-Label

Moderate-Range

Moderate-Label

USG-Range

USG-Label

Unhealthy-Range

Unhealthy-Label

VeryUnhealthy-Range

VeryUnhealthy-Label

Hazardous-Range

Hazardous-Label

Pollutant-Title

Ozone-Title

Ozone-Text

PM25-Title

PM25-Text

Use two fingers to pan the map

Air Quality Forecast and Spare the Air Alerts

Air is almost always on the move, and pollution can easily drift from one reporting zone to another. This is particularly true in the Bay Area, which forms a single air basin, and where winds can blow pollution from one location into neighboring valleys.

That is why a Spare the Air Alert is called for the entire Bay Area when air quality is forecast to be unhealthy in any one of the five reporting zones: North Counties, Coast and Central Bay, Eastern Zone, South Central Bay, and Santa Clara Valley.

Reporting zones are different from county lines: they are defined by air current patterns and geographic features that lead to shared air quality within certain areas.

The Air District issues a daily forecast that predicts air pollution levels for the coming five-day period. The forecast uses the U.S. EPA’s Air Quality Index to indicate how healthy or unhealthy those air pollution levels are expected to be.

A Spare the Air Alert is called when air quality is forecast to be unhealthy, or above 100 in the AQI, in any one of the reporting zones. An alert may span over two days if air quality is expected to remain unhealthy for prolonged periods.

If air quality is unhealthy in the Bay Area, it is almost always because of two kinds of air pollutants: Ozone and fine particulate matter, or PM2.5.

The daily forecast is available by signing up for email ‌AirAlerts or calling the Air District’s 24-hour, toll-free information line (1-800-HELP AIR).