SAN FRANCISCO — Wednesday is shaping up to be the hottest day of the week in much of San Francisco, but the city will not heat evenly.
The National Weather Service has a Heat Advisory in effect from 10 a.m. Wednesday through 10 p.m. Thursday. A representative NWS point forecast in central San Francisco reaches about 87°F Wednesday, while a point near the far western edge of the city is closer to 78°F. That roughly nine-degree spread is a useful reminder that "San Francisco temperature" can mean very different conditions depending on where you are.
For people deciding whether to commute, exercise outside, take children to the park or simply find somewhere cooler, here is the practical San Francisco-specific forecast.
How hot will San Francisco get Wednesday?
Wednesday is the clear peak in the current NWS forecast for central San Francisco. The city forecast calls for morning clouds giving way to sun and a high around 87°F. Wednesday night stays relatively mild, with a low around 65°F.
By Thursday, the central-city forecast falls sharply to about 77°F, and Friday is near 71°F. The advisory nevertheless remains in force through 10 p.m. Thursday because the warning covers a broader area and heat impacts can persist beyond the single hottest afternoon.
Which parts of San Francisco will be hottest?
Local terrain and the marine influence matter. Representative NWS point forecasts available Tuesday morning show the warmer readings concentrated farther from the immediate coast, while western neighborhoods remain noticeably cooler.
| Representative area | Wednesday forecast high | What it means |
|---|---|---|
| Central / Mission-area point | About 87°F | Among the warmer NWS point forecasts inside San Francisco. |
| Castro / central-west point | About 84°F | Still hot by San Francisco standards, but a few degrees below the warmest central point. |
| Northwest / inner-west point | About 82°F | Marine influence begins to shave several degrees off the inland-city heat. |
| Far western SF near Ocean Beach | About 78°F | Cooler than central SF, though still warm for the immediate coast. |
These are point forecasts, not hard neighborhood boundaries. A few blocks, elevation and afternoon wind can change the temperature. But the pattern is useful: the coast should be the cooler side of the city Wednesday.
What are the hottest hours?
San Francisco's Department of Public Health advises people to get out of the heat especially between 10 a.m. and 4 p.m., when conditions are generally hottest. If you need to exercise, walk a dog or do outdoor work, earlier morning or later evening is the safer part of the day.
Heat can be deceptively stressful in San Francisco because many homes were built for a cool coastal climate and do not have air conditioning. Check on older adults, young children and anyone with medical conditions that make heat harder to tolerate.
Where can you cool off in San Francisco?
The San Francisco Public Library maintains a list of library spaces designated for cooling during extreme heat. Three locations have air conditioning throughout the building:
- Main Library — 100 Larkin Street
- Chinatown/Him Mark Lai Branch — 1135 Powell Street
- Mission Bay Branch — 960 4th Street
SFPL also lists limited-capacity cooled spaces at Ortega, Park, Portola, Presidio, Richmond, Visitacion Valley, Potrero, North Beach and Glen Park branches. Check the branch's current opening hours before leaving; the cooling-center designation does not by itself mean a branch has special extended hours for this advisory.
If a library is inconvenient, SFDPH also recommends spending time in another air-conditioned public location such as a shopping center.
Is Ocean Beach a good place to escape the heat?
The forecast supports the basic idea that the immediate west side should be cooler: the far-west NWS point forecast is around 78°F Wednesday versus roughly 87°F in central San Francisco.
But a cooler beach is not automatically a risk-free place. Conditions at Ocean Beach can include cold water, strong surf, wind and sudden fog. Treat it as a temperature break, not as a substitute for checking current beach conditions.
When does San Francisco cool down?
The sharpest relief arrives Thursday in the current central-city forecast, which drops from roughly 87°F Wednesday to about 77°F Thursday. Friday is forecast near 71°F.
Forecasts can move as the marine layer and wind pattern change. The figures in this article were checked against NWS point forecasts on the morning of Sept. 8 and should be treated as a planning guide rather than a guarantee for every block.
Heat safety in practical terms
Drink water before you feel thirsty, take breaks in shade or air conditioning, avoid leaving people or pets in parked vehicles, and seek medical help for signs of serious heat illness such as confusion, fainting or a very high body temperature.
For current conditions, use the National Weather Service San Francisco forecast. For cooling locations, see the San Francisco Public Library cooling-center list. SFDPH's 2026 heat resources sheet has additional health guidance.