Air District Operations

The Air District is taking steps to ensure Bay Area air quality and public health are protected while the shelter-in-place orders are in effect. Permits for businesses adjusting operations to aid in the public health response will also be expedited. Read more... | en Español

About the Air District

San Mateo County

About the Air District

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
  • May

    May 29, 2020

    Air District releases latest Ambient Air Monitoring Network Report

    The Air District has released its latest Ambient Air Monitoring Network Report, which describes the Air District’s air monitoring network for 2019, and lists proposed changes for the near future.

  • May

    May 28, 2020

    South Coast AQMD Files Lawsuit Challenging Trump Administration Rollbacks to Clean Vehicle Standards

    Today, the South Coast Air Quality Management District filed a petition challenging the U.S. EPA and the National Highway Traffic Safety Administration’s rollbacks to the Safer Affordable Fuel-Efficient Vehicles Rule initiated by the Trump Administration. The Bay Area Air Quality Management District and the Sacramento Metropolitan Air Quality Management District have joined South Coast AQMD as co-petitioners.

  • May

    May 24, 2020

    Air District issues first Spare the Air Alert for smog this year

    Today, the Bay Area Air Quality Management District is issuing the first Spare the Air Alert for smog in 2020. Air quality is forecast to be unhealthy tomorrow, Memorial Day, Monday, May 25. Light winds combined with triple-digit inland temperatures and vehicle exhaust are expected to cause unhealthy smog, or ozone, accumulation in the Bay Area.

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
No Wood Burning
Spare the Air Status
  • Saturday,

    No Spare the Air Alert in Effect

Last Updated: 2/14/2019