How do we measure air quality?
One of the most common ways to measure air quality is by measuring particulate matter, or PM. PM refers to extremely small particles in the air that are detrimental to your health. PM2.5, also called “fine particulates,” consists of particles with diameters ≤ 2.5 microns. PM10 refers to “coarse particles” that have a diameter ≤ 10 microns. To learn more about PM, click here.
Air Quality Monitoring Data
Weather conditions and winds change dramatically during the winter months in the Bay Area. Frequently cool windless days will occur and an inversion layer sets in, a phenomenon when cooler air sinks and warm air aloft traps the air in our region. This causes air pollutants that we emit every day from driving, farming, industrial activities, and burning wood in fireplaces to build up and become trapped in the air.
Periodically, the Bay Area Air Quality Management District (BAAQMD) forecast higher particulate matter concentrations in the North Bay. This is often due to cooler temperatures in the North and the inland valleys and often trapped wood smoke pollution.
The winter weather pattern will continue intermittently throughout Napa, Sonoma, and Marin counties. By late February to early March, this pattern will switch to a spring weather pattern allowing for more air disbursement.
For Sebastopol: To find information on the most recent PM2.5 air quality data, please click here.
For Cloverdale, Healdsburg, and Guerneville: To find information on the most recent Air Quality Index (AQI) by the Northern Sonoma County Air Pollution Control District, please click here.
Five-day forecast: If you’d like to see the current spare the air status and five-day forecast, please click here.
For map predictions, click on the forecast here.
The Bay Area Air Quality Management District developed this legend to help you understand the PM2.5 data. As established by the U.S. Environmental Protection Agency (EPA), the Air Quality Index for PM2.5 is based on 24-hour concentrations, so hourly readings are only estimates.
|Air Quality Index Levels of Health Concern||Numerical Value|
|Good||0 to 50|
|Moderate||51 to 100|
|Unhealthy for Sensitive Groups||101 to 150|
|Unhealthy||151 to 200|
|Very Unhealthy||201 to 300|
|Hazardous||301 to 500|
*This website is actively being developed and updated with additional information. Information is subject to change.
Please see below for answers to many frequently asked questions. An additional resource is available here.
There are three categories of air quality data that are available:
- Routinely collected air quality data from fixed monitors from the Bay Area Air Quality Management District (BAAQMD) and Northern Sonoma County Air Pollution Control District (NSCAPCD).
- Supplemental air quality data from recently placed mobile monitors. This includes California Air Resources Board monitors placed at Sonoma County schools located near debris sites.
- Debris site monitoring conducted by US Army Corps of Engineers.