The Environmental Protection Agency has an air quality index for many California cities, and the private company PurpleAir maintains an interactive, crowdsourced air quality map.
Officials across the Bay Area are urging people to check on neighbors, and are publishing lists of libraries and other shelters for those looking to cool down:
San Francisco
The San Francisco Recreation and Park Department is waiving admission fees to seven pools throughout the city today.
Midday lap swims and lessons will continue as scheduled and at least one lane will be designated to accommodate those who are at the pool for heat relief.
The information on the schedules of the seven pools included is:
Balboa Pool
51 Havelock St.
10 a.m. – 2:30 p.m.: one lane available for free heat relief
3 p.m. – 4 p.m.: free recreation swim
6:30 p.m. – 8 p.m.: small pool available for free heat relief
Coffman Pool
1700 Visitacion Ave.
10 a.m. – 1 p.m.: one lane available for free heat relief
2:45 p.m. – 3:45 p.m.: free recreation swim
7:30 p.m. – 8:30 p.m.: free family swim
Hamilton Pool
1900 Geary Blvd.
10 a.m. – 1 p.m.: small pool available for free heat relief
2 p.m. – 3 p.m. free recreation swim
MLK Pool
5701 3rd St.
10:30 a.m. – 12:30 p.m.: one lane available for free heat relief
3 p.m. – 4 p.m.: free recreation swim
6:30 p.m. – 7:30 p.m.: one lane available for free heat relief
Mission Pool
101 Linda St.
10:30 a.m. – 1:30 p.m.: one lane available for free heat relief
3 p.m. – 4:30 p.m.: free recreation swim
North Beach Pool
651 Lombard St
10 a.m. – 11:30 a.m.: one lane available for free heat relief
12:00 p.m. – 1:30 p.m.: one lane available for free heat relief
3:30 p.m. – 4:30 p.m.: free recreation swim
5:45 p.m. – 7 p.m.: free recreation swim
Sava Pool
2695 19th Ave.
9:30 a.m. -11 a.m.: one lane available for free heat relief
12:00 p.m. – 2 p.m.: one lane available for free heat relief
2 p.m. – 3:30 p.m.: free recreation swim
6:30 p.m. – 8:30 p.m.: free recreation swim
San Jose
Temperatures in the upper 90s are expected for the San Jose area on Friday. Five local community centers will extend their hours of operation until 9 p.m. to provide indoor buildings to beat the heat.
The centers listed by the Department of Parks, Recreation and Neighborhood Services are the following:
Mayfair Community Center
2039 Kammerer Ave.
Roosevelt Community Center
901 E. Santa Clara St.
Camden Community Center
3369 Union Ave.
Cypress
Community Center
403 Cypress Ave.
Seven Trees Community Center
3590 Cas Drive
City of Santa Clara
Central Park Library
2635 Homestead Rd.
City Hall Cafeteria
1500 Warburton Ave.
Community Recreation Center
969 Kiely Blvd.
Senior Center
1303 Fremont St.
Northside Branch Library
695 Moreland Way
Mission Branch Library
1098 Lexington St.
East Bay
Alameda County Healthcare for the Homeless maintains a list of cooling centers in Berkeley, Oakland, Alameda, Albany, Emeryville, and elsewhere in the East Bay, which you can find here.
San Leandro
(Open until 7 p.m. Friday)
Marina Community Center
15301 Wicks Blvd.
Main Library
300 Estudillo Ave.