San Francisco weather in May

In May, San Francisco sees average daytime highs of 25°C and overnight lows near 18°C, with 333 mm of rain across 24.7 wet days and about 12.5 hours of daylight. It is the 3rd-warmest and 5th-wettest month of the year here.

Day-to-day highs hold fairly steady near 25°C through the month. The sky is clear or mostly clear about 2% of the time in May, and the air most often feels humid.

Daylight stretches from about 12 h 18 min at the start of May to 12 h 30 min by month's end. Set against the rest of the year, May is San Francisco's 7th-clearest and 9th-windiest month. For the whole year in context, see San Francisco's year-round climate.

Daytime high
25°
3rd warmest
Overnight low
18°
12th coldest
Rainfall
333 mm
24.7 wet days
Daylight
12 h 30 min
5:19 AM – 5:46 PM
Cloud cover
89%
7th clearest
Wind
5 km/h
9th windiest
Solar energy
4.44 kWh/m²
Travel score
4.2
out of 10

Temperature in May

Average highAverage lowShaded bands: 10–90% of days

Day-to-day highs hold fairly steady near 25°C through the month.

A typical May day in San Francisco reaches about 25°C in the afternoon and slips back to 18°C overnight — a 7°C spread between the day's warmth and the night's chill. On most days the high lands between 23°C and 27°C. Set against its neighbours, May runs about 1°C cooler than April and on par with June.

15°20°25°30°151015202531
Avg high (°C)Avg low (°C)
12618
22618
32618
42618
52618
62618
72618
82618
92618
102618
112618
122618
132518
142518
152518
162518
172518
182518
192518
202518
212518
222518
232518
242518
252518
262518
272518
282518
292518
302518
312518

San Francisco weather by month

How May compares with the rest of the year at a glance. May is the 3rd-warmest and 5th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysDaylight (hours)Travel score
Jan25° / 16°295.811.57.8
Feb25° / 16°204.111.78.0
Mar26° / 17°205.211.97.5
Apr27° / 17°6211.212.26.2
May25° / 18°33324.712.54.2
Jun25° / 18°39027.312.63.8
Jul24° / 18°2672512.54.3
Aug25° / 18°35226.412.34.0
Sep24° / 17°42428.312.13.7
Oct24° / 17°44428.811.83.8
Nov24° / 17°22421.511.54.8
Dec24° / 17°7210.811.46.9

Cloud cover in May

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 2% of the time in May.

Beyond those clear spells, partly cloudy skies cover about 4% of May, with mostly cloudy or overcast conditions the remaining 94%.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
11486
21486
31189
41189
51189
61090
71090
81090
9991
10892
11892
12793
13793
14793
15694
16595
17595
18496
19496
20496
21397
22397
23397
24397
25397
26397
27298
28298
29397
30397
31397

Chance of precipitation in May

Any precipitation

San Francisco gets around 333 mm of rain over 24.7 wet days in May. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 80% and peaks near 93% on the wettest days. The odds climb toward the end of the month.

0%20%40%60%80%100%151015202531
Rain chance (%)
158
259
361
462
563
665
767
868
970
1072
1174
1276
1378
1480
1581
1683
1785
1886
1987
2088
2189
2290
2390
2491
2592
2692
2793
2893
2993
3093
3193

Humidity in May

DryComfortableHumidMuggyOppressiveMiserable

Most of May feels humid — the stacked bands show each day's mix of comfort levels, read off the dew point.

By dew point, May lands in the humid band about 50% of days. Sticky, muggy-or-worse air turns up on roughly 45% of them.

0%25%50%75%100%151015202531
Dry (%)Comfortable (%)Humid (%)Muggy (%)
11176616
21166617
31146718
41136620
51126621
61116523
7196624
8196426
9186328
10176230
11066133
12065935
13055738
14045541
15045244
16035146
17034849
18024652
19024454
20024256
21024157
22013960
23013762
24013663
25013564
26013366
27013267
28013168
29003070
30003070
31002971

Wind in May

Winds average 5 km/h in May.

Across May, daily wind ranges from about 4 km/h on the calmest days to 5 km/h at its breeziest. It stays fairly steady from day to day.

0246810151015202531
Wind speed (km/h)Feels
15calm
25calm
35calm
45calm
55calm
65calm
75calm
85calm
95calm
105calm
115calm
125calm
135calm
145calm
155calm
165calm
175calm
185calm
195calm
204calm
214calm
224calm
234calm
244calm
254calm
264calm
274calm
284calm
294calm
304calm
314calm

Sunrise & sunset in May

DaylightNight

Daylight runs from about 12 h 18 min at the start of May to 12 h 30 min by month's end. The lit band spans sunrise to sunset each day.

Days grow by about 12 minutes over May. Sunrise moves from 5:23 AM to 5:18 AM, and sunset from 5:44 PM to 5:50 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
112.35:235:44
212.45:235:44
312.45:235:44
412.45:225:44
512.45:225:45
612.45:225:45
712.45:215:45
812.45:215:45
912.45:215:45
1012.45:205:45
1112.45:205:46
1212.45:205:46
1312.45:205:46
1412.45:195:46
1512.55:195:46
1612.55:195:46
1712.55:195:47
1812.55:195:47
1912.55:195:47
2012.55:185:47
2112.55:185:48
2212.55:185:48
2312.55:185:48
2412.55:185:48
2512.55:185:48
2612.55:185:49
2712.55:185:49
2812.55:185:49
2912.55:185:49
3012.55:185:50
3112.55:185:50

Solar energy in May

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in May, about 4.44 kWh/m².

For context, solar energy here swings from a low near 3.65 kWh/m² to a high of 5.95 kWh/m² in March across the year — May's 4.44 kWh/m² falls in the middle.

0246151015202531
Solar energy (kWh/m²)Level
15.0Bright
25.0Bright
34.9Bright
44.9Bright
54.8Bright
64.8Bright
74.8Bright
84.7Bright
94.7Bright
104.6Bright
114.6Bright
124.5Bright
134.5Bright
144.5Bright
154.4Bright
164.4Bright
174.3Bright
184.3Bright
194.3Bright
204.3Bright
214.2Bright
224.2Bright
234.2Bright
244.2Bright
254.2Bright
264.2Bright
274.2Bright
284.2Bright
294.2Bright
304.2Bright
314.2Bright
Planning a trip in May

Hazard calendar for San Francisco

In seasonPeak

In May, San Francisco sits inside its rainy season season. The full year is below, with each hazard's peak months called out.

San Francisco's rainy season runs May–November, when most of the year's rain falls.

Rainy season
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec

Is May a good time to visit San Francisco?

Our two travel scores rate May for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal).

4.2
Sightseeing
8th-best month of the year
4.0
Beach & pool
7th-best month of the year

May is a reasonable time to visit San Francisco for sightseeing.

What to pack for San Francisco in May

From May's temperature range, rain chance, sun and wind — what's worth putting in the bag.

In May, San Francisco sees daytime highs around 25°C and nights near 18°C. Pack rain gear. Worth having: light clothes. About 25 days see rain.

rain gearlight clothes

Sea temperature near San Francisco in May

The nearest coast averages about 29°C in May — the other half of the beach question. The full-year curve and swim-comfort zones are below.

The sea at the nearest coast (about 56 km away) is warmest in April at about 29°C and coldest in November near 28°C.

The water stays above 20°C all year — warm enough for a swim any month.

26°28°30°JanFebMarAprMayJunJulAugSepOctNovDecwarmtropicalcomfortable to swim
Sea temperature (°C)Comfort
Jan29Tropical
Feb29Tropical
Mar29Tropical
Apr29Tropical
May29Tropical
Jun29Tropical
Jul29Tropical
Aug29Tropical
Sep29Tropical
Oct28Tropical
Nov28Warm
Dec28Tropical

UV index in San Francisco in May

LowModerateHighVery highExtreme

Clear-sky midday UV in May peaks around 13 (very high — sun protection essential). The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in San Francisco peaks around March 19 at about 15 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 16 at about 10 (extreme).

The index reaches 3 or more — the level where the WHO recommends sun protection — every month of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecExtremeMar 19UV 15Dec 16UV 10
UV index (midday)Level
Jan12Extreme
Feb14Extreme
Mar15Extreme
Apr14Extreme
May13Extreme
Jun13Extreme
Jul13Extreme
Aug13Extreme
Sep13Extreme
Oct12Extreme
Nov12Extreme
Dec10Extreme

Air quality in San Francisco in May

GoodModeratePoorUnhealthyVery unhealthy

Average fine-particle pollution (PM2.5) through the year — so you can see where May falls, not just the annual average.

Air quality in San Francisco is worst in May — around 19 µg/m³ PM2.5 (moderate), about 2.1× the cleanest month (January, 9 µg/m³).

Modeled monthly averages (CAMS reanalysis, 2015–2024).

0102030JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodMay 1718 µg/m³Jan 149 µg/m³
PM2.5 (µg/m³)Level
Jan9Good
Feb10Good
Mar11Good
Apr17Moderate
May19Moderate
Jun17Moderate
Jul18Moderate
Aug17Moderate
Sep16Moderate
Oct14Moderate
Nov12Good
Dec10Good
Location & terrain

Where is San Francisco?

San Francisco sits at 10.0°N, 84.1°W, 1,131 m above sea level, in Costa Rica. The nearest listed city is Heredia, 1.0 km away.

Topography around San Francisco

How much the land rises and falls, and what covers it, within 3, 16 and 80 km of San Francisco.

Within 3 km, the terrain around San Francisco has significant variations in elevation — a maximum elevation change of 271 m around an average of 1,102 m above sea level; within 16 km, very significant variations in elevation — a maximum elevation change of 2,296 m; within 80 km, extreme variations in elevation — a maximum elevation change of 3,470 m.

The land around San Francisco is covered by artificial surfaces (68%) and trees (22%) within 3 km, trees (56%) and artificial surfaces (29%) within 16 km, and trees (70%) within 80 km.

3 km
271 m
16 km
2,296 m
80 km
3,470 m
treesgrasslandcroplandartificial surfaceswater
May weather nearby: Heredia 1.0 km · Mercedes Norte 1.0 km · San Pablo 3.0 km · San Juan 6.0 km · Colima 7.0 km · San Rafael 7.0 km · San Jose 8.0 km · Calle Blancos 9.0 km

Costa Rica travel facts

Travel advisory
Level 2
Exercise Increased Caution
Power plugs
Type A / B
120 V · 60 Hz
Prices
≈ 59% of US
price level, 2025
GDP per capita
$19,970
2025
Happiness
7.4 / 10
World Happiness, 2025
Safe drinking water
81%
of population, 2024
Homicide rate
17.7
per 100k, 2023
Road deaths
14.8
per 100k/yr, 2019
Income group
High
World Bank
English
Moderate
EF EPI 516
Religion
Roman Catholic 48%none 27%Evangelical and Pentecostal 20%other 3%

Sources: World Bank, US State Department, World Happiness Report, WHO/UNICEF, EF EPI, CIA World Factbook.

Data sources

Temperature, precipitation, cloud, humidity, wind and solar figures are a 1991–2020 climatology for San Francisco (9.9938°, -84.1274°, elevation 1,131 m), computed from hourly ERA5 reanalysis — contains modified Copernicus Climate Change Service information. Sun figures are astronomical calculations, not observations. City data © GeoNames, CC BY 4.0. Map outlines from Natural Earth (public domain); interactive map © Google. Sea temperatures are the NOAA OISST v2.1 1991–2020 monthly climatology (public domain), sampled at the nearest ocean point. UV index is derived from CAMS (Copernicus Atmosphere Monitoring Service) clear-sky UV data — contains modified Copernicus Atmosphere Monitoring Service information. Monthly air-quality (PM2.5) seasonality is from the CAMS EAC4 reanalysis (Copernicus Atmosphere Monitoring Service), scaled to the WHO annual mean where available. Topography is sampled from the Copernicus DEM GLO-90 elevation model (© ESA/Airbus) and ESA WorldCover 2021 land cover (CC BY 4.0).