Changes focus on improving efficiency and delivering timely, transparent permit decisions.
Learn about Sonoma County - its climate, potential air pollution concerns, and current air quality. You can also view upcoming Air District events in Sonoma County and read about local efforts to improve air quality.
Sonoma County lies to the west of Lake and Napa counties, north of Marin County, and south of Mendocino County. The Air District only has jurisdiction over the southern portion of the county, which includes Santa Rosa, Petaluma, and Sonoma. Two Sonoma County representatives sit on the Air District’s Board of Directors.
Changes focus on improving efficiency and delivering timely, transparent permit decisions.
The Air District has fined Chemtrade West US LLC $160,000 for air quality violations at its sulfuric acid manufacturing plant in Richmond, which is connected to the Chevron Richmond refinery. Chemtrade supplies various chemical products to industry, including sulfuric acid, which is a byproduct of refining crude oil.
The Air District is lifting an air quality advisory for wildfire smoke that was originally scheduled to last through tomorrow, Wednesday, August 27.
The Air District has announced a $13.3 million grant to the San Mateo County Transit District toward the installation of new high-capacity electric bus charging infrastructure at its San Carlos facility. This SamTrans project will help accelerate the transition of the SamTrans bus fleet to zero-emission technology and improve air quality in communities most affected by air pollution.
August 21, 2025
August 19, 2025
August 18, 2025
August 14, 2025
August 12, 2025
August 11, 2025
July 30, 2025
July 28, 2025
July 23, 2025
July 17, 2025
July 14, 2025
Sonoma County’s climate is largely affected by the topography of the Petaluma, Cotati, and Sonoma valleys. Temperatures are similar in the Petaluma and Cotati valleys, while Sonoma Valley temperatures are warmer, similar to Napa Valley. Average daily temperatures range from moderate overnight to hot during the day in the summer, and cool overnight to moderate during the day in the winter. Wind patterns in the Petaluma and Cotati valleys are strongly influenced by the Petaluma Gap, with calm to mild winds typical in both Santa Rosa and Petaluma. During late afternoons in summer, fog is common in the Petaluma and Cotati valleys, and can persist until late morning the following day. Sunshine in the Sonoma Valley is plentiful. Annual rainfall ranges from 24 inches in Petaluma, 29 inches in Sonoma, and 30 inches in Santa Rosa.
Interactive Air Monitoring Stations Map
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.
Although much of the interior of Sonoma County can get quite hot during summer, air monitoring results show that this area experiences some of the lowest ozone levels in the entire Bay Area. Gaps in the hills to the west allow fresh marine air inland on all but the hottest summer days.
PM2.5 can become elevated, particularly due to wood burning during the holiday season, but once again, air monitoring results show that this region has some of the lowest levels of PM2.5 in the entire Bay Area.
Last Updated: 4/21/2017