During summer, ozone and fine particles from sources to our west occasionally degrade Yosemite air quality. Sometimes, smoke from local or regional fires also contribute. By the end of September though, ozone usually diminishes due to lower levels due to cooler fall temperatures, lower angle sunlight, and shorter days. Fires continue to occur in the fall before (or until) the rains come—as late as December in a dry year. Check back and scroll down to see the most current information on air quality and smoke impacts in Yosemite.
Yosemite National Park monitors smoke/fine particles and ozone as part of a nationwide effort to protect air quality and public health. Various agencies in California provide statewide smoke information. Current nationwide conditions are mapped below. NOAA also has a map showing smoke plumes.