May in San Francisco is dry, bright and cool: the downtown station averages a high of 64.1°F (17.8°C), a low of 51.4°F (10.8°C) and 0.70 inch of rain on about 4 days. Afternoons are windy, the ocean is at its coldest, and foggy mornings become common on the west side.
May averages a high only about a degree warmer than April. Yet San Francisco hit 97°F on May 15, 2008, just 2 degrees short of the hottest July day on record, 99°F on July 3, 1931. May is a month of quiet averages and sudden exceptions.
What Is May Weather Like in San Francisco?
May weather in San Francisco is the last clear window before summer fog. The rain is nearly done, the days are long and bright, and most afternoons stay in the low to mid 60s downtown. At the same time, the wind and fog that define a San Francisco summer are switching on, and the ocean reaches its coldest point of the year. Visitors who picture late spring in California get the dry, sunny part right. They usually miss how cool and breezy it feels.
| Average high / low | 64.1°F (17.8°C) / 51.4°F (10.8°C) |
|---|---|
| Average rain | 0.70 in (18 mm) on about 4 days |
| Days at 70°F or warmer | About 5 |
| Afternoon wind | Windy; about 17 mph at 2 PM at Crissy Field |
| Foggy mornings | Building on the west side; about 1 in 4 early-morning hours in the Outer Sunset |
| Ocean temperature | About 52°F offshore, the coldest of the year |
| Sunset | About 8:00 PM on May 1, 8:25 PM on May 31 |
San Francisco Downtown station (USW00023272), NOAA 1991-2020 normals via RCC-ACIS. Wind and fog from NOAA High-Resolution Rapid Refresh (HRRR) model analysis, September 2014 to April 2026. Ocean temperature from the NOAA NCEI Coastal Water Temperature Guide (buoy 46026). Sunset times computed for 2027.
Is It Still Rainy in San Francisco in May?
San Francisco is barely rainy in May. The month averages 0.70 inch on about 4 days, and 87% of May days are dry. The last meaningful rain of the season, 0.10 inch or more in a day, comes around May 24 in a typical year, so the rainy season is effectively over by Memorial Day.
Late storms still happen. May 2019 brought 1.94 inches and May 2023 brought 1.21, while May 2017 recorded none at all. The wettest May on record had 4.02 inches, in 1925. From 1991 to 2020, about 1 May in 10 had no measurable rain, and 7 in 10 had at least a tenth of an inch. See how the rainy season winds down and the wetter month before in San Francisco weather in April.
As the storms end, the ocean and the wind take over.
Why Are May Afternoons So Windy, and the Ocean So Cold?
May afternoons are windy and the ocean is cold because of two linked effects. As the North Pacific High builds offshore, strong northwest winds along the coast push surface water away from shore and pull cold deep water up, a process called upwelling. Meanwhile, the warming inland valleys draw a strong sea breeze through the Golden Gate every afternoon.
In NOAA's HRRR model analysis from 2014 to 2026, the average 2 PM wind at Crissy Field is about 17 mph in May, up from about 15 mph in April, and three of every four afternoon hours reach 15 mph or more. Downtown averages a gentler 10 to 11 mph. Read more about the North Pacific High and spring winds.
The ocean off San Francisco bottoms out at about 52.4°F in May, the coldest month of the year, while the shallow bay at Alameda warms past 63°F. In practice, that means a wetsuit for any swim at Ocean Beach, a calmer bay-side beach for wading, and a jacket for anywhere shaded or on the water. For year-round numbers, see Bay Area water temperatures.
When Does the Fog Come Back in May?
Fog comes back to the west side first, and May is when it starts to stick. In NOAA's HRRR model analysis from 2014 to 2026, fog covered the Outer Sunset in about 1 in 4 early-morning hours in May, up from about 1 in 6 in April and heading toward 2 in 5 in June. Downtown stays clearer. In May 2025 alone, the model showed fog on 65% of mornings in the Outer Sunset and 39% downtown.
Locals call it May Gray: mornings start gray at the coast and usually clear toward the bay by midday. Downtown, May fog is mostly a morning event, covering about 15% of 7 AM hours but only about 2% of 2 PM hours. In the Outer Sunset it can hang on, at about 1 in 4 hours both morning and afternoon. The neighborhoods east of Twin Peaks see the most sun. See San Francisco weather by neighborhood for where the fog lingers, and the Bay Area fog forecast for tomorrow.
Can San Francisco Get Hot in May?
San Francisco can get hot in May, but only occasionally, when the sea breeze shuts off and offshore winds blow warm air from inland toward the coast. A typical May has about one day at 80°F or warmer downtown (1.3 days on average from 1991 to 2020). Nearly two Mays in three reached 80°F at least once in that period, and about one in six reached 90°F.
The record is 97°F on May 15, 2008, followed by 92°F the next day. More recently, Memorial Day 2020 hit 81°F. These heat spikes are short: the fog and wind usually return within a day or two. For the bigger picture, see Bay Area heat waves and the hottest temperatures on record.
What Is the Weather Like for Bay to Breakers, Carnaval and Memorial Day?
Bay to Breakers is a morning race on the third Sunday in May, and its course runs west from near the Embarcadero to Ocean Beach, so runners finish where morning fog is most likely. In HRRR analysis, fog covers the Outer Sunset in about 25% of 7 AM hours in May, against 15% downtown. Third Sundays of May average a high of 65.9°F, and measurable rain fell on only 12% of them from 1950 to 2025.
Carnaval San Francisco fills the Mission District over Memorial Day weekend. The Mission is one of the warmest, sunniest parts of the city in May: in HRRR analysis, it averages about 66°F at 3 PM, roughly 7 degrees warmer than downtown. Bring sun protection as well as a layer for the evening.
Memorial Day itself averages a high of 65.1°F and a low of 51.8°F, and it has rained on only about 1 in 11 of them since 1950. For reliable warmth, head inland: Walnut Creek averages about 74°F on May afternoons in HRRR analysis. See how much colder San Francisco is than inland.
Is May a Good Time to Visit San Francisco?
May is a good time to visit San Francisco if you want dry, bright days and long evenings without the deep summer fog. Sunset moves from about 8:00 PM on May 1 to 8:25 PM on May 31, and days grow from about 13.8 to 14.6 hours. Expect cool, windy afternoons, plan beach time for the sunny breaks, and pack a windproof jacket over a light sweater. Mornings near the ocean and evenings anywhere run in the low 50s, so a warm layer earns its place in the bag even on a sunny day. June is about 2 degrees warmer downtown but noticeably foggier; compare it in San Francisco weather in June, or see the best month to visit.
Before a May day out, check the San Francisco forecast for afternoon wind and the fog forecast to see whether the west side is clearing. If you want sun, compare the Mission District with Ocean Beach before you pick a spot.