Air Quality Forecast

Sunday, December 15
Fri
Sat
Sun
Mon
Tue
Northern Zone
50
55
57
72
M
Coast and Central Bay
57
42
53
61
M
Eastern Zone
46
46
50
61
M
South Central Bay
38
40
42
53
M
Santa Clara Valley
42
39
46
50
G
Last Updated: Friday, December 13 at 10:58 AM

How the Forecast Affects Alerts

Air is almost always on the move, and it is easy for pollution to drift from one reporting zone to another. This is particularly true in the Bay Area where winds can blow pollution from one location into neighboring valleys.

That is why a Spare the Air Alert or Winter Spare the Air Alert is called for the whole 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. A Spare the Air Alert or Winter Spare the Air Alert is called the day before air quality is forecast to be unhealthy in any one of the reporting zones. An alert may span over two days if air quality is expected to remain unhealthy.

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).