12 Sep 2020. Pacific Coast. San Francisco’s air quality index (AQI): 186 (Atlantic Coast – Boston: 14). Unprecedented.

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San Francisco, along with Sebastapol in the North Bay, recorded an AQI of 186, the worst daily air quality of any other location in the past 25 days when the Bay Area has been impacted by smoke from record-breaking wildfires across the West Coast.

The Air Quality Index operates on a scale from 0 to 500. The higher the AQI value, the greater the level of air pollution and the greater the health concern. An AQI value of 50 or below represents good air quality, while an AQI value over 300 signals hazardous conditions.

The highest daily AQI ever measured in San Francisco was 228 on Nov. 16, 2018, when smoke from the Camp Fire near Chico flooded the city. A daily AQI is an average of the hourly readings across 24 hours. On Nov. 16, 2018, S.F. had its highest-ever hourly reading of 271. On Thursday, AQI in the city peaked at 238.

More than 500 firefighters and four helicopters were battling the El Dorado blaze east of San Bernardino, which started Saturday morning, California Department of Forestry and Fire Protection (Cal Fire) said.

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