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South San Francisco, California climate
Csb Warm-summer Mediterranean
South San Francisco has a mildly seasonal mild-temperate climate (Warm-summer Mediterranean, Köppen Csb). The hottest month is September with an average daily high near 75°F, while the coldest is January averaging around 45°F at night. Precipitation totals about 20 inches a year and is strongly seasonal — December alone averages 4.1 inches while July barely receives 0.00 inches.
Temperature & precipitation
Daily high–low temperature range with the monthly average, plus monthly precipitation · 1991–2020 normals · hover a month for the exact figuresClear vs cloudy days
Share of days each month that are clear, partly cloudy or cloudy · 1991–2020 · hover a month for the day countsSouth San Francisco climate normals (1991–2020)
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high (°F) | 58 | 61 | 63 | 66 | 68 | 72 | 73 | 73 | 75 | 72 | 64 | 58 |
| Avg temp (°F) | 51 | 54 | 56 | 57 | 60 | 63 | 64 | 65 | 65 | 63 | 56 | 51 |
| Avg low (°F) | 45 | 46 | 48 | 49 | 52 | 54 | 55 | 56 | 56 | 53 | 49 | 45 |
| Precipitation (in) | 3.9 | 4.0 | 2.7 | 1.4 | 0.5 | 0.1 | 0.0 | 0.0 | 0.1 | 0.8 | 2.0 | 4.1 |
| Jan – Jun | Jan | Feb | Mar | Apr | May | Jun |
|---|---|---|---|---|---|---|
| Avg high (°F) | 58 | 61 | 63 | 66 | 68 | 72 |
| Avg temp (°F) | 51 | 54 | 56 | 57 | 60 | 63 |
| Avg low (°F) | 45 | 46 | 48 | 49 | 52 | 54 |
| Precipitation (in) | 3.9 | 4.0 | 2.7 | 1.4 | 0.5 | 0.1 |
| Jul – Dec | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|
| Avg high (°F) | 73 | 73 | 75 | 72 | 64 | 58 |
| Avg temp (°F) | 64 | 65 | 65 | 63 | 56 | 51 |
| Avg low (°F) | 55 | 56 | 56 | 53 | 49 | 45 |
| Precipitation (in) | 0.0 | 0.0 | 0.1 | 0.8 | 2.0 | 4.1 |
How often — frequency of weather events
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Days with measurable rain (days) | 11 | 11 | 10 | 6 | 3 | 1 | 0.0 | 0.4 | 0.9 | 3 | 7 | 11 |
| Days with high ≥ 90°F (days) | — | — | — | 0.1 | 0.4 | 0.7 | 0.3 | 0.6 | 2 | 0.5 | — | — |
| Days with low ≤ 32°F (days) | 0.0 | — | — | — | — | — | — | — | — | — | — | 0.1 |
| Jan – Jun | Jan | Feb | Mar | Apr | May | Jun |
|---|---|---|---|---|---|---|
| Days with measurable rain (days) | 11 | 11 | 10 | 6 | 3 | 1 |
| Days with high ≥ 90°F (days) | — | — | — | 0.1 | 0.4 | 0.7 |
| Days with low ≤ 32°F (days) | 0.0 | — | — | — | — | — |
| Jul – Dec | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|
| Days with measurable rain (days) | 0.0 | 0.4 | 0.9 | 3 | 7 | 11 |
| Days with high ≥ 90°F (days) | 0.3 | 0.6 | 2 | 0.5 | — | — |
| Days with low ≤ 32°F (days) | — | — | — | — | — | 0.1 |
Sky & atmosphere
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Cloud cover (%) | 60 | 61 | 60 | 55 | 54 | 48 | 58 | 59 | 51 | 47 | 51 | 57 |
| Clear days (≤ 30% cloud) | 7 | 6 | 7 | 8 | 8 | 10 | 4 | 4 | 9 | 11 | 10 | 8 |
| Partly cloudy days (30–70%) | 9 | 8 | 11 | 11 | 11 | 11 | 15 | 14 | 11 | 11 | 10 | 9 |
| Cloudy days (≥ 70%) | 15 | 14 | 14 | 11 | 12 | 9 | 12 | 13 | 10 | 9 | 10 | 14 |
| Relative humidity (%) | 84 | 83 | 84 | 84 | 85 | 85 | 86 | 86 | 83 | 80 | 80 | 81 |
| Wind speed (mph) | 8.0 | 8.6 | 8.5 | 9.0 | 8.9 | 8.7 | 7.5 | 7.3 | 6.7 | 6.6 | 7.2 | 8.4 |
| Jan – Jun | Jan | Feb | Mar | Apr | May | Jun |
|---|---|---|---|---|---|---|
| Cloud cover (%) | 60 | 61 | 60 | 55 | 54 | 48 |
| Clear days (≤ 30% cloud) | 7 | 6 | 7 | 8 | 8 | 10 |
| Partly cloudy days (30–70%) | 9 | 8 | 11 | 11 | 11 | 11 |
| Cloudy days (≥ 70%) | 15 | 14 | 14 | 11 | 12 | 9 |
| Relative humidity (%) | 84 | 83 | 84 | 84 | 85 | 85 |
| Wind speed (mph) | 8.0 | 8.6 | 8.5 | 9.0 | 8.9 | 8.7 |
| Jul – Dec | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|
| Cloud cover (%) | 58 | 59 | 51 | 47 | 51 | 57 |
| Clear days (≤ 30% cloud) | 4 | 4 | 9 | 11 | 10 | 8 |
| Partly cloudy days (30–70%) | 15 | 14 | 11 | 11 | 10 | 9 |
| Cloudy days (≥ 70%) | 12 | 13 | 10 | 9 | 10 | 14 |
| Relative humidity (%) | 86 | 86 | 83 | 80 | 80 | 81 |
| Wind speed (mph) | 7.5 | 7.3 | 6.7 | 6.6 | 7.2 | 8.4 |
30-year delta table (1991–2020 minus 1981–2010, °F)
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Δ Max temp | +1.7 | +1.3 | +1.3 | +0.9 | +0.7 | +0.9 | +0.6 | +0.7 | +1.2 | +1.9 | +1.4 | +1.6 |
| Δ Avg temp | +1.0 | +0.6 | +0.6 | +0.4 | +0.3 | +0.3 | +0.3 | +0.4 | +0.6 | +1.1 | +0.6 | +0.8 |
| Δ Min temp | +0.3 | -0.2 | -0.1 | +0.0 | +0.0 | -0.2 | -0.1 | +0.1 | +0.1 | +0.2 | -0.2 | +0.0 |
| Jan – Jun | Jan | Feb | Mar | Apr | May | Jun |
|---|---|---|---|---|---|---|
| Δ Max temp | +1.7 | +1.3 | +1.3 | +0.9 | +0.7 | +0.9 |
| Δ Avg temp | +1.0 | +0.6 | +0.6 | +0.4 | +0.3 | +0.3 |
| Δ Min temp | +0.3 | -0.2 | -0.1 | +0.0 | +0.0 | -0.2 |
| Jul – Dec | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|
| Δ Max temp | +0.6 | +0.7 | +1.2 | +1.9 | +1.4 | +1.6 |
| Δ Avg temp | +0.3 | +0.4 | +0.6 | +1.1 | +0.6 | +0.8 |
| Δ Min temp | -0.1 | +0.1 | +0.1 | +0.2 | -0.2 | +0.0 |
Methodology & sources
Temperature & precipitation — the official 1991–2020 climate normals from NOAA's U.S. Climate Normals, measured at San Francisco Intl AP (NOAA GHCN station USW00023234), about 5 km from the city centre.
Cloud, humidity, wind & sunshine — modelled estimates from NASA POWER, NASA's satellite-and-reanalysis climatology. This is the standard global source for atmospheric variables, which are not measured at most weather stations.