SAN FRANCISCO — San Francisco remains under a National Weather Service Heat Advisory through Thursday night, but the city is forecast to be substantially cooler than it was Wednesday.
The NWS advisory remains scheduled to expire at 10 p.m. Thursday, Sept. 10. Representative point forecasts around the city call for highs mostly in the low-to-upper 70s Thursday, followed by another step down Friday.
That means the practical question has changed from “how hot will Wednesday get?” to when does the advisory end and how quickly does San Francisco cool off?
When does the San Francisco Heat Advisory end?
The National Weather Service keeps the Heat Advisory in effect until 10 p.m. Thursday.
That expiration time can still be changed if conditions warrant, so anyone making heat-sensitive plans later Thursday should check the current NWS hazard banner rather than relying solely on an older screenshot or forecast.
How hot will San Francisco get Thursday?
A current NWS point forecast near central San Francisco calls for a high around 75°F, while another representative point is near 77°F. A point farther southwest is around 73°F.
Those numbers are substantially below Wednesday’s hottest readings, when parts of the city reached the upper 80s. San Francisco’s hills, ocean influence and wind can still produce noticeable differences over short distances.
When does cooler weather return?
The cooldown is already underway Thursday and becomes more obvious Friday. Current NWS point forecasts put Friday highs around the upper 60s to low 70s, with west or southwest winds.
For most people, that means Friday should feel much closer to a typical mild San Francisco day than Wednesday did.
Do you still need to take heat precautions Thursday?
Yes, particularly if you are in a warm indoor space, working outdoors or are sensitive to heat. Many San Francisco homes do not have air conditioning, and indoor temperatures can remain elevated after a hot day.
Drink water, take breaks in shade or cooler indoor spaces, avoid leaving children or pets in parked vehicles, and check on people who may have difficulty regulating body temperature.
Where can you cool off?
San Francisco Public Library maintains cooling information for library spaces. The Main Library, Chinatown/Him Mark Lai Branch and Mission Bay Branch have air conditioning throughout the building, while some other branches have limited cooled areas.
Check current branch hours before leaving. A library listed as a cooling location does not necessarily have extended hours for this advisory.
Will the west side stay cooler?
Generally, the current point forecasts continue to show cooler conditions in parts of the city that are more exposed to ocean influence, but there is no single temperature that describes every San Francisco neighborhood.
If you head toward the coast to cool off, remember that beach hazards are separate from heat. Cold water, currents, sneaker waves, fog and wind can still be dangerous on a warm city day.