About the Air District

Contra Costa County

Learn about Contra Costa County - its climate, potential air pollution concerns, and current air quality. You can also view upcoming Air District events in Contra Costa County and read about local efforts to improve air quality.

Contra Costa County lies east of the San Pablo Bay, bounded by Alameda County to the south, San Joaquin County to the east, and Solano and Sacramento counties to the north. Four representatives sit on the Air District’s Board of Directors.

Latest News
  • Jan

    January 12, 2021

    Air District’s Charge! Program offers $6 million for electric vehicle charging stations

    The Air District is announcing the availability of $6 million through the Charge! program, which provides grant funding to offset the cost of purchasing and installing new publicly accessible chargers for light-duty electric vehicles.

  • Dec

    December 28, 2020

    Air District settles case with Chevron USA Inc.

    The Air District announced today that Chevron USA Inc. has agreed to pay $147,000 to settle violations at its refinery in Richmond. This settlement covers 29 Notices of Violation issued for air quality violations at the Richmond oil refinery during 2016 – 2018.

  • Dec

    December 21, 2020

    Spare the Air Alert extended through Tuesday due to wood smoke buildup

    The Air District is issuing the winter season’s third Spare the Air Alert for tomorrow, Tuesday, December 22, which bans burning wood, manufactured fire logs or any other solid fuel, both indoors and outdoors. Smoke from increased wood burning is expected to cause air quality to be unhealthy with the heaviest impacts in the Santa Clara Valley due to cold overnight temperatures and light winds.


Temperatures in and around the San Ramon and Diablo Valleys are warm in the summer and cool in the winter, largely because of their distance from the moderating effect of water bodies and because the California Coast Range blocks marine air flow into the valleys. The Carquinez Strait region remains temperate due to its proximity to water and oceanic air flows. In winter, average daily temperatures are mild, with tule fog common at night. Average summer temperatures are typically mild overnight and warm during the day, with cooler temperatures and stronger winds more common along the western coast. Wind speeds are generally low throughout the region and winds typically blow from northwest to southwest. However, strong afternoon gusts are common in the northern portion of the county around the Carquinez Strait. Annual rainfall averages between 18 and 23 inches across the county.

Contra Costa County’s climate is also affected by regional Bay Area climate influences.

Interactive Air Monitoring Stations Map

Air Quality in Contra Costa County

Ozone and fine particle pollution, or PM2.5, are the major regional air pollutants of concern in the San Francisco Bay Area. Ozone is primarily a problem in the summer, and fine particle pollution in the winter.

Ozone and PM2.5 infrequently exceed health standards in the portion of Contra Costa County west of the East Bay hills. The San Francisco Bay keeps air temperatures above freezing in winter and well below 100 degrees on even the warmest summer days. 

In eastern Contra Costa County, summer afternoon temperatures frequently approach triple digits, spurring ozone levels to exceed health standards. In winter, PM2.5 can be transported westward through the Carquinez Strait from the Central Valley where it adds to wood smoke, causing health standards to be exceeded.

Interactive Air Quality Forecast Map

Resource Team

Contra Costa County’s Spare the Air Resource Team promotes various ways to reduce air pollution in the local community.

Spare the Air Status

Last Updated: 2/14/2019