https://www.mercurynews.com/2020/08/20/how-to-measure-smoke-levels-in-your-neighborhood-from-california-wildfires/

With dozens of major fires burning from Wine Country to the Santa Cruz Mountains, Salinas to the Mount Hamilton foothills, smoke levels are bad across the Bay Area and Northern California. Breathing it can harm your health.

There are several websites to find real-time information about air quality and smoke levels in your community. All of the sites use the U.S. Environmental Protection Agency’s Air Quality Index, which ranks air pollution levels on a 0-500 scale, with green and yellow being the best, and red and purple the worst.