About the Air District

San Mateo County

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

Latest News
  • Jan

    January 12, 2022

    Air District settles case with Air Liquide

    The Air District announced today that Air Liquide Large Industries, US LP, has agreed to pay $159,000 to settle violations that occurred at its hydrogen plant at the San Francisco Oil Refinery in Rodeo.

  • Jan

    January 11, 2022

    First meeting of Air District’s Community Advisory Council to be held January 13

    The Air  District’s Community Advisory Council will hold its first meeting January 13 at 6 PM. In a historic moment, the Air District Board of Directors approved the formation of the Air District’s first Community Advisory Council on November 17, 2021. The Community Advisory Council will advise the Air District’s Board of Directors on environmental justice and equity-based policy and is the first body of its kind at the Bay Area Air District.

  • Jan

    January 5, 2022

    Air District’s Climate Tech Finance program funds acceleration of electric vehicle adoption

    The Air District has awarded a loan guarantee to EvGateway, an electric vehicle solutions management company focused on accelerating the adoption and use of electric vehicles by making them easier to use.

San Mateo County lies in the middle of the San Francisco Peninsula, south of San Francisco County, and north of Santa Clara and Santa Cruz counties. It is bounded by the Pacific Ocean to the west and San Francisco Bay to the east. Two San Mateo County representatives sit on the Air District’s Board of Directors.


Cool, foggy weather is prevalent along the western coast of the peninsula, particularly during the summer. Summertime average daily temperatures are moderate along the west coast and warm in the county’s east side. In the winter, average daily temperatures across the county range from mild to moderate. Winds are mild, with the highest wind speeds focused along the western coast. Rainfall averages about 20 to 25 inches per year at lower elevations and up to 36 inches in the Santa Cruz Mountains.

San Mateo County's climate is also affected by regional Bay Area climate influences.

Interactive Air Monitoring Stations Map

Air Quality in San Mateo 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.

In San Mateo County, ozone almost never exceeds health standards, and PM2.5 exceeds the national standard only on about one day each year. San Mateo County frequently receives fresh marine air from the Pacific Ocean, which passes over the coastal hills. In winter, PM2.5 may be transported into San Mateo County from other parts of the Bay Area, adding to wood smoke, which may lead to elevated concentrations, but these are rarely high enough to exceed health standards.

Interactive Air Quality Forecast Map

Resource Team

San Mateo County's Spare the Air Resource Team promotes ways to reduce air pollution in the local community.

Spare the Air Status

Last Updated: 2/14/2019