Climate and average weather in San Francisco
In San Francisco, the weather is warm, wet, and partly cloudy and remarkably steady, with daytime highs holding near warm levels all year. The wettest stretch peaks around October.
Over the course of the year, the temperature in San Francisco typically varies from 16°C to 27°C, and is rarely below 14°C or above 28°C. April is the hottest month of the year, while November is the coldest.
Based on the travel score, the best times of year to visit San Francisco for warm-weather activities are from early January to mid April and mid December to late December.
- Hottest
- Apr
- 27°
- Coldest
- Nov
- 17°
- Wettest
- Oct
- 444 mm
- Driest
- Feb
- 20 mm
- Rain / yr
- 2635 mm
- 219 wet days
- Daylight
- 11.4–12.6 h
- shortest–longest
- Elevation
- 1,131 m
- 10.0°N
- Clearest
- Feb
- 43% cloud
San Francisco weather by month, at a glance
The whole year in one picture — sky, rain, humidity, temperature and travel score. Click any band to jump to its full chart.
Each stripe is one measure across the whole year, stacked so a single day reads top to bottom. The sky band runs overcast grey on top down to clear blue at the base — more blue means sunnier — followed by the rainfall curve, the humidity band, a temperature strip that tints each stretch of the year by how warm its average high is, and the travel-score line at the foot. Scan straight down any date to read that day across every measure at once; the score climbs highest around early January to mid April.
Temperature through the year
Daily average highs and lows in San Francisco, from 1991–2020 of climate data. The shaded bands show the range most days fall in — 10th to 90th percentile.
Temperatures in San Francisco stay fairly even through the year, without a distinct hot or cool season. The warmest month is April, with an average high of 27°C and low of 17°C; the coolest is November, with an average low of 17°C and high of 24°C.
Days typically run about 8°C warmer than nights year-round.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high (°C) | 25 | 25 | 26 | 27 | 25 | 25 | 24 | 25 | 24 | 24 | 24 | 24 |
| Avg low (°C) | 16 | 16 | 17 | 17 | 18 | 18 | 18 | 18 | 17 | 17 | 17 | 17 |
| Avg high (°C) | Avg low (°C) | |
|---|---|---|
| Jan | 25 | 16 |
| Feb | 25 | 16 |
| Mar | 26 | 17 |
| Apr | 27 | 17 |
| May | 25 | 18 |
| Jun | 25 | 18 |
| Jul | 24 | 18 |
| Aug | 25 | 18 |
| Sep | 24 | 17 |
| Oct | 24 | 17 |
| Nov | 24 | 17 |
| Dec | 24 | 17 |
Average hourly temperature in San Francisco
A compact picture of the whole year, hour by hour: each column is a day, each row an hour, and the color is the modeled average temperature. Darker overlays mark night, lighter ones the civil-twilight hours around sunrise and sunset.
Read left to right for the day of the year and top to bottom for the hour of the day; the color is the modeled temperature, cool blues through to hot reds on the same scale as the other charts. A vertical slice is a single day's swing — coolest just before dawn, warmest in the mid-afternoon — while a horizontal slice follows one hour across the seasons. The darker overlay marks night and the lighter one the twilight around sunrise and sunset. Colors run warmest on April afternoons, near 27°C, and coldest before dawn in November, near 17°C.
San Francisco weather by month
Every month at a glance. Click a month for its detailed page.
| Month | High / Low (°C) | Rainfall (mm) | Wet days | Daylight (hours) | Travel score |
|---|---|---|---|---|---|
| Jan | 25° / 16° | 29 | 5.8 | 11.5 | 7.8 |
| Feb | 25° / 16° | 20 | 4.1 | 11.7 | 8.0 |
| Mar | 26° / 17° | 20 | 5.2 | 11.9 | 7.5 |
| Apr | 27° / 17° | 62 | 11.2 | 12.2 | 6.2 |
| May | 25° / 18° | 333 | 24.7 | 12.5 | 4.2 |
| Jun | 25° / 18° | 390 | 27.3 | 12.6 | 3.8 |
| Jul | 24° / 18° | 267 | 25 | 12.5 | 4.3 |
| Aug | 25° / 18° | 352 | 26.4 | 12.3 | 4.0 |
| Sep | 24° / 17° | 424 | 28.3 | 12.1 | 3.7 |
| Oct | 24° / 17° | 444 | 28.8 | 11.8 | 3.8 |
| Nov | 24° / 17° | 224 | 21.5 | 11.5 | 4.8 |
| Dec | 24° / 17° | 72 | 10.8 | 11.4 | 6.9 |
Chance of rain
How likely it is to rain on a typical day, and how that shifts across the wetter and drier seasons.
San Francisco gets about 2635 mm of precipitation a year. On a typical day the chance of rain is very wet, but that rises and falls sharply with the seasons.
The wetter season lasts 6.8 months, from around May 3 to Nov 25, peaking in September at about 96% chance on a given day. The drier stretch runs the rest of the year, bottoming out around Feb 1.
October is the wettest month by volume, with 444 mm over about 29 wet days; February is the driest, with 20 mm.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Rain on a day (%) | 19 | 14 | 18 | 37 | 79 | 90 | 81 | 85 | 94 | 92 | 71 | 36 |
| Rain days | 6 | 4 | 5 | 11 | 25 | 27 | 25 | 26 | 28 | 29 | 22 | 11 |
| Rain on a day (%) | Rain days | |
|---|---|---|
| Jan | 19 | 6 |
| Feb | 14 | 4 |
| Mar | 18 | 5 |
| Apr | 37 | 11 |
| May | 79 | 25 |
| Jun | 90 | 27 |
| Jul | 81 | 25 |
| Aug | 85 | 26 |
| Sep | 94 | 28 |
| Oct | 92 | 29 |
| Nov | 71 | 22 |
| Dec | 36 | 11 |
Monthly rainfall
Over a full year, San Francisco collects about 2635 mm of rain across 219 wet days — roughly 220 mm in an average month.
It doesn’t fall evenly. October is the wettest month with 444 mm, while February is the driest at just 20 mm. The three wettest months alone bring about 48% of the year’s total.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Rainfall (mm) | 29 | 20 | 20 | 62 | 333 | 390 | 267 | 352 | 424 | 444 | 224 | 72 |
| Rain days | 6 | 4 | 5 | 11 | 25 | 27 | 25 | 26 | 28 | 29 | 22 | 11 |
| Rainfall (mm) | Rain days | |
|---|---|---|
| Jan | 29 | 6 |
| Feb | 20 | 4 |
| Mar | 20 | 5 |
| Apr | 62 | 11 |
| May | 333 | 25 |
| Jun | 390 | 27 |
| Jul | 267 | 25 |
| Aug | 352 | 26 |
| Sep | 424 | 28 |
| Oct | 444 | 29 |
| Nov | 224 | 22 |
| Dec | 72 | 11 |
Clouds and sunshine
How often the daytime sky is clear, partly cloudy or overcast.
In San Francisco, the average share of the sky covered by clouds shows significant seasonal variation over the course of the year.
The clearer part of the year begins around November 26 and lasts for 4.8 months, ending around April 20. The clearest month is February, when the sky is clear, mostly clear, or partly cloudy 76% of the time on average.
The cloudier part of the year begins around April 21 and lasts for 7.2 months, ending around November 25. The cloudiest month is September, when it is overcast or mostly cloudy 98% of the time.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Clearer (%) | 72 | 76 | 66 | 36 | 7 | 3 | 5 | 4 | 2 | 4 | 19 | 54 |
| Cloudier (%) | 28 | 24 | 34 | 64 | 93 | 97 | 95 | 96 | 98 | 96 | 81 | 46 |
| Clearer (%) | Cloudier (%) | |
|---|---|---|
| Jan | 72 | 28 |
| Feb | 76 | 24 |
| Mar | 66 | 34 |
| Apr | 36 | 64 |
| May | 7 | 93 |
| Jun | 3 | 97 |
| Jul | 5 | 95 |
| Aug | 4 | 96 |
| Sep | 2 | 98 |
| Oct | 4 | 96 |
| Nov | 19 | 81 |
| Dec | 54 | 46 |
Daylight, sunrise and sunset
Hours of daylight through the year, with sunrise and sunset times.
The gold band is daylight — sunrise runs along its lower edge, sunset along the upper — so it widens toward summer and pinches toward winter, with night the dark area above and below. The longest day, around June 4, brings about 12 h 36 min of light; the shortest, around January 1, only 11 h 24 min — a swing of roughly 1 h 12 min.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Daylight (h) | 11.5 | 11.7 | 11.9 | 12.2 | 12.5 | 12.6 | 12.5 | 12.3 | 12.1 | 11.8 | 11.5 | 11.4 |
| Sunrise (AM) | 6:02 | 6:01 | 5:48 | 5:30 | 5:19 | 5:19 | 5:26 | 5:31 | 5:29 | 5:28 | 5:36 | 5:50 |
| Sunset (PM) | 5:30 | 5:41 | 5:44 | 5:43 | 5:46 | 5:54 | 5:58 | 5:51 | 5:32 | 5:15 | 5:08 | 5:15 |
| Daylight (h) | Sunrise (AM) | Sunset (PM) | |
|---|---|---|---|
| Jan | 11.5 | 6:02 | 5:30 |
| Feb | 11.7 | 6:01 | 5:41 |
| Mar | 11.9 | 5:48 | 5:44 |
| Apr | 12.2 | 5:30 | 5:43 |
| May | 12.5 | 5:19 | 5:46 |
| Jun | 12.6 | 5:19 | 5:54 |
| Jul | 12.5 | 5:26 | 5:58 |
| Aug | 12.3 | 5:31 | 5:51 |
| Sep | 12.1 | 5:29 | 5:32 |
| Oct | 11.8 | 5:28 | 5:15 |
| Nov | 11.5 | 5:36 | 5:08 |
| Dec | 11.4 | 5:50 | 5:15 |
Sunny days
How many genuinely sunny days each month brings — days the sky stays clear or mostly clear — banded into plain-language zones.
San Francisco averages about 5 sunny days a month — counting the days the sky stays clear or mostly clear — with a clear seasonal swing between 0 and 16 days.
The sunnier stretch runs 4.5 months, from around Nov 30 to Apr 16. The sunniest month is February, with roughly 15 sunny days (bright).
The greyest month is June, down near 0 sunny days — about 99% fewer than the February peak.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sunny days | 14 | 14 | 12 | 5 | 1 | 0 | 0 | 0 | 0 | 0 | 2 | 9 |
| Sky | Mixed | Bright | Mixed | Gloomy | Gloomy | Gloomy | Gloomy | Gloomy | Gloomy | Gloomy | Gloomy | Mixed |
| Sunny days | Sky | |
|---|---|---|
| Jan | 14 | Mixed |
| Feb | 14 | Bright |
| Mar | 12 | Mixed |
| Apr | 5 | Gloomy |
| May | 1 | Gloomy |
| Jun | 0 | Gloomy |
| Jul | 0 | Gloomy |
| Aug | 0 | Gloomy |
| Sep | 0 | Gloomy |
| Oct | 0 | Gloomy |
| Nov | 2 | Gloomy |
| Dec | 9 | Mixed |
Humidity comfort
Share of days at each humidity comfort level, based on the dew point — the measure that tracks how muggy it actually feels.
Humidity comfort is graded by the dew point — the temperature at which the air would be fully saturated — because it tracks how muggy it actually feels far better than relative humidity does. A low dew point feels dry and crisp; a high one feels sticky and oppressive no matter the reading on a humidity gauge.
In San Francisco, how humid it feels changes dramatically over the year.
The more humid part of the year lasts 7.4 months, from around April 27 to December 7. The muggiest month is June, when the air feels humid, muggy or worse about 100% of the time.
The most comfortable stretch runs from around December 8 to April 26, and February is the most comfortable month — the air is dry or comfortable 79% of the time.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Dry (%) | 10 | 17 | 13 | 6 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 |
| Comfortable (%) | 65 | 61 | 60 | 37 | 6 | 0 | 1 | 0 | 0 | 0 | 6 | 37 |
| Humid (%) | 25 | 20 | 25 | 52 | 49 | 37 | 64 | 65 | 57 | 59 | 75 | 58 |
| Muggy (%) | 0 | 1 | 2 | 5 | 45 | 63 | 35 | 35 | 43 | 41 | 19 | 3 |
| Dry (%) | Comfortable (%) | Humid (%) | Muggy (%) | |
|---|---|---|---|---|
| Jan | 10 | 65 | 25 | 0 |
| Feb | 17 | 61 | 20 | 1 |
| Mar | 13 | 60 | 25 | 2 |
| Apr | 6 | 37 | 52 | 5 |
| May | 0 | 6 | 49 | 45 |
| Jun | 0 | 0 | 37 | 63 |
| Jul | 0 | 1 | 64 | 35 |
| Aug | 0 | 0 | 65 | 35 |
| Sep | 0 | 0 | 57 | 43 |
| Oct | 0 | 0 | 59 | 41 |
| Nov | 0 | 6 | 75 | 19 |
| Dec | 1 | 37 | 58 | 3 |
Wind
Average wind speed through the year, banded into plain-language speed zones so a number reads as 'breezy' or 'calm' without knowing the scale.
This is the average sustained wind speed at the standard 10 metres above open ground — the steady flow a weather station reports, not the sharper gusts that come and go, which can run half again as fast. It's the number that says whether a place is generally breezy or calm.
Across the year, average wind speed in San Francisco is typically calm, near 6 km/h, and varies moderately with the seasons.
The windier part of the year lasts 4.8 months, from around Nov 19 to Apr 13. The windiest month is February, averaging about 9 km/h (calm).
The calmer part of the year runs from around Apr 14 to Nov 18, with September the calmest month at about 4 km/h.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Wind speed (km/h) | 9 | 9 | 8 | 6 | 5 | 5 | 6 | 5 | 4 | 4 | 6 | 8 |
| Feels | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm | calm |
| Wind speed (km/h) | Feels | |
|---|---|---|
| Jan | 9 | calm |
| Feb | 9 | calm |
| Mar | 8 | calm |
| Apr | 6 | calm |
| May | 5 | calm |
| Jun | 5 | calm |
| Jul | 6 | calm |
| Aug | 5 | calm |
| Sep | 4 | calm |
| Oct | 4 | calm |
| Nov | 6 | calm |
| Dec | 8 | calm |
Hazard calendar for San Francisco
When the seasonal hazards worth planning around — the rainy season, tropical-cyclone risk and dust haze — are active through the year.
San Francisco's rainy season runs May–November, when most of the year's rain falls.
Best time to visit San Francisco
To characterize how pleasant the weather is in San Francisco throughout the year, we compute two travel scores — one for general sightseeing, one for beach and pool weather.
Around early April, San Francisco is still near the tail of its best-weather window — great conditions with the peak-season crowds already thinning.
Inferred from the travel-score curve; month-by-month visitor numbers are a planned addition.
The travel score favors clear, rainless days with daytime highs between 18°C and 28°C. Based on this score, the best time of year to visit San Francisco for general outdoor tourist activities is from mid December to mid April, with a peak score in the last week of January.
The travel score (filled area), and its constituents: the temperature score (red line), the cloud cover score (blue line), and the precipitation score (green line).
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Travel score (0–10) | 7.8 | 8.0 | 7.5 | 6.2 | 4.2 | 3.8 | 4.2 | 4.0 | 3.7 | 3.8 | 4.9 | 6.8 |
| Rating | ideal | ideal | good | good | fair | fair | fair | fair | fair | fair | fair | good |
| Travel score (0–10) | Rating | |
|---|---|---|
| Jan | 7.8 | ideal |
| Feb | 8.0 | ideal |
| Mar | 7.5 | good |
| Apr | 6.2 | good |
| May | 4.2 | fair |
| Jun | 3.8 | fair |
| Jul | 4.2 | fair |
| Aug | 4.0 | fair |
| Sep | 3.7 | fair |
| Oct | 3.8 | fair |
| Nov | 4.9 | fair |
| Dec | 6.8 | good |
The beach/pool score favors clear, rainless days with daytime highs between 24°C and 34°C. Based on this score, the best time of year to visit San Francisco for hot-weather activities is from mid December to late April, with a peak score in the first week of March.
The beach/pool score (filled area), and its constituents: the temperature score (red line), the cloud cover score (blue line), and the precipitation score (green line).
What to pack for San Francisco, by month
Month by month, what's worth putting in the bag — from the temperature range, rain chance, sun and wind. Tap a month for a quick packing note.
San Francisco packs about the same all year — highs hold near 27°C. Across the year the things worth having are light clothes, rain gear and sun protection.
In April, San Francisco sees daytime highs around 27°C and nights near 17°C. Worth packing: light clothes, rain gear and sun protection. About 11 days see rain.
Sea temperature near San Francisco
Average ocean temperature at the nearest coast, month by month, banded into swim-comfort zones — the other half of the beach question.
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.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sea temperature (°C) | 29 | 29 | 29 | 29 | 29 | 29 | 29 | 29 | 29 | 28 | 28 | 28 |
| Comfort | Tropical | Tropical | Tropical | Tropical | Tropical | Tropical | Tropical | Tropical | Tropical | Tropical | Warm | Tropical |
| Sea temperature (°C) | Comfort | |
|---|---|---|
| Jan | 29 | Tropical |
| Feb | 29 | Tropical |
| Mar | 29 | Tropical |
| Apr | 29 | Tropical |
| May | 29 | Tropical |
| Jun | 29 | Tropical |
| Jul | 29 | Tropical |
| Aug | 29 | Tropical |
| Sep | 29 | Tropical |
| Oct | 28 | Tropical |
| Nov | 28 | Warm |
| Dec | 28 | Tropical |
UV index (midday) in San Francisco by month
Clear-sky midday UV index through the year, shaded by the WHO exposure levels — how much sun protection each month calls for.
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.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UV index (midday) | 12 | 14 | 15 | 14 | 13 | 13 | 13 | 13 | 13 | 12 | 12 | 10 |
| Level | Extreme | Extreme | Extreme | Extreme | Extreme | Extreme | Extreme | Extreme | Extreme | Extreme | Extreme | Extreme |
| UV index (midday) | Level | |
|---|---|---|
| Jan | 12 | Extreme |
| Feb | 14 | Extreme |
| Mar | 15 | Extreme |
| Apr | 14 | Extreme |
| May | 13 | Extreme |
| Jun | 13 | Extreme |
| Jul | 13 | Extreme |
| Aug | 13 | Extreme |
| Sep | 13 | Extreme |
| Oct | 12 | Extreme |
| Nov | 12 | Extreme |
| Dec | 10 | Extreme |
Average hourly UV index in San Francisco
Modeled clear-sky UV for every hour of every day — when in the day sun protection actually matters.
The whole year hour by hour: each column is a day, each row an hour, and the color is the modeled clear-sky UV index — the midday peak scaled down as the sun sits lower in the sky. Darker overlays mark night, lighter ones the civil-twilight hours around sunrise and sunset.
UV falls off far faster than brightness as the sun drops, so even in March the burn window is concentrated in the middle of the day: about 8.5 hours a day reach index 3 (protection recommended), and 6.5 hours reach 6 or more. Mornings and late afternoons stay comparatively gentle year round.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UV ≥ 3 (h/day) | 7.5 | 8 | 8.5 | 8 | 8.5 | 8.5 | 8.5 | 8 | 8 | 7.5 | 7.5 | 7 |
| UV ≥ 6 (h/day) | 5.5 | 6 | 6.5 | 6.5 | 6.5 | 6.5 | 6.5 | 6.5 | 6.5 | 5.5 | 5.5 | 5 |
| UV ≥ 3 (h/day) | UV ≥ 6 (h/day) | |
|---|---|---|
| Jan | 7.5 | 5.5 |
| Feb | 8 | 6 |
| Mar | 8.5 | 6.5 |
| Apr | 8 | 6.5 |
| May | 8.5 | 6.5 |
| Jun | 8.5 | 6.5 |
| Jul | 8.5 | 6.5 |
| Aug | 8 | 6.5 |
| Sep | 8 | 6.5 |
| Oct | 7.5 | 5.5 |
| Nov | 7.5 | 5.5 |
| Dec | 7 | 5 |
Air quality in San Francisco by month
Average fine-particle pollution (PM2.5) through the year — so you can see which months the air is worst, not just the yearly 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).
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| PM2.5 (µg/m³) | 9 | 10 | 11 | 17 | 19 | 17 | 18 | 17 | 16 | 14 | 12 | 10 |
| Level | Good | Good | Good | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Good | Good |
| PM2.5 (µg/m³) | Level | |
|---|---|---|
| Jan | 9 | Good |
| Feb | 10 | Good |
| Mar | 11 | Good |
| Apr | 17 | Moderate |
| May | 19 | Moderate |
| Jun | 17 | Moderate |
| Jul | 18 | Moderate |
| Aug | 17 | Moderate |
| Sep | 16 | Moderate |
| Oct | 14 | Moderate |
| Nov | 12 | Good |
| Dec | 10 | Good |
Growing season
San Francisco is frost-free year round — even the coldest nights rarely reach freezing, so there is no start or end to the growing season.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Frost-free chance (%) | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 |
| Frost nights | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| Frost-free chance (%) | Frost nights | |
|---|---|---|
| Jan | 100 | 0 |
| Feb | 100 | 0 |
| Mar | 100 | 0 |
| Apr | 100 | 0 |
| May | 100 | 0 |
| Jun | 100 | 0 |
| Jul | 100 | 0 |
| Aug | 100 | 0 |
| Sep | 100 | 0 |
| Oct | 100 | 0 |
| Nov | 100 | 0 |
| Dec | 100 | 0 |
Growing degree days
Growing degree days tally heat above 10°C: each day adds however many degrees its average temperature runs over that threshold, and cold days add nothing. San Francisco banks about 4,001 degree days a year, and the running total — which growers use to time plantings and predict maturity — climbs fastest around April.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Growing degree days (°C·days) | 321 | 302 | 354 | 358 | 359 | 336 | 343 | 341 | 323 | 327 | 313 | 323 |
| Growing degree days (°C·days) | |
|---|---|
| Jan | 321 |
| Feb | 302 |
| Mar | 354 |
| Apr | 358 |
| May | 359 |
| Jun | 336 |
| Jul | 343 |
| Aug | 341 |
| Sep | 323 |
| Oct | 327 |
| Nov | 313 |
| Dec | 323 |
Solar energy
Average daily shortwave solar energy reaching the ground, banded into brightness zones so the number means something at a glance.
Solar energy is how much sunlight actually reaches the ground each day, measured in kilowatt-hours per square metre (kWh/m²) — the combined effect of how long the sun is up, how high it climbs, and how much cloud gets in the way. It's the raw fuel a solar panel has to work with: for scale, 1 kWh/m² a day is dim and wintry, while 7+ is desert-bright.
San Francisco receives about 4.6 kWh/m² a day of solar energy on average — bright — with a clear seasonal swing between 3.7 and 6.0 kWh/m².
The brighter stretch of the year lasts 4.2 months, from around Jan 3 to May 10. The brightest month is March, averaging about 5.9 kWh/m² (bright).
The dimmest month is November, down near 3.7 kWh/m² — roughly 38% less than the March peak.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Solar energy (kWh/m²) | 4.9 | 5.5 | 6.0 | 5.7 | 4.4 | 4.2 | 4.2 | 4.4 | 4.3 | 3.8 | 3.6 | 4.2 |
| Level | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Bright | Moderate | Moderate | Bright |
| Solar energy (kWh/m²) | Level | |
|---|---|---|
| Jan | 4.9 | Bright |
| Feb | 5.5 | Bright |
| Mar | 6.0 | Bright |
| Apr | 5.7 | Bright |
| May | 4.4 | Bright |
| Jun | 4.2 | Bright |
| Jul | 4.2 | Bright |
| Aug | 4.4 | Bright |
| Sep | 4.3 | Bright |
| Oct | 3.8 | Moderate |
| Nov | 3.6 | Moderate |
| Dec | 4.2 | Bright |
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.
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
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).