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Clayton, California climate
Csb Warm-summer Mediterranean
Clayton has a mildly seasonal mild-temperate climate (Warm-summer Mediterranean, Köppen Csb). The hottest month is September with an average daily high near 25°C, while the coldest is December averaging around 6°C at night. Precipitation totals about 663 mm a year and is strongly seasonal — December alone averages 135 mm while July barely receives 0 mm.
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 countsClayton climate normals (1991–2020)
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high (°C) | 15 | 16 | 18 | 20 | 21 | 23 | 23 | 24 | 25 | 23 | 18 | 15 |
| Avg temp (°C) | 11 | 12 | 13 | 14 | 15 | 17 | 18 | 18 | 18 | 17 | 13 | 11 |
| Avg low (°C) | 6 | 7 | 8 | 8 | 10 | 11 | 12 | 12 | 12 | 11 | 8 | 6 |
| Precipitation (mm) | 123 | 130 | 98 | 46 | 20 | 7 | 0 | 1 | 3 | 30 | 70 | 135 |
| Jan – Jun | Jan | Feb | Mar | Apr | May | Jun |
|---|---|---|---|---|---|---|
| Avg high (°C) | 15 | 16 | 18 | 20 | 21 | 23 |
| Avg temp (°C) | 11 | 12 | 13 | 14 | 15 | 17 |
| Avg low (°C) | 6 | 7 | 8 | 8 | 10 | 11 |
| Precipitation (mm) | 123 | 130 | 98 | 46 | 20 | 7 |
| Jul – Dec | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|
| Avg high (°C) | 23 | 24 | 25 | 23 | 18 | 15 |
| Avg temp (°C) | 18 | 18 | 18 | 17 | 13 | 11 |
| Avg low (°C) | 12 | 12 | 12 | 11 | 8 | 6 |
| Precipitation (mm) | 0 | 1 | 3 | 30 | 70 | 135 |
How often — frequency of weather events
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Days with measurable rain (days) | 10 | 10 | 9 | 7 | 3 | 1 | 0.3 | 0.5 | 1.0 | 3 | 7 | 10 |
| Days with high ≥ 32°C (days) | — | — | — | 0.2 | 0.6 | 1 | 0.4 | 0.7 | 2 | 0.8 | — | — |
| Days with low ≤ 0°C (days) | 0.4 | 0.0 | — | — | — | — | — | — | — | — | — | 0.3 |
| Jan – Jun | Jan | Feb | Mar | Apr | May | Jun |
|---|---|---|---|---|---|---|
| Days with measurable rain (days) | 10 | 10 | 9 | 7 | 3 | 1 |
| Days with high ≥ 32°C (days) | — | — | — | 0.2 | 0.6 | 1 |
| Days with low ≤ 0°C (days) | 0.4 | 0.0 | — | — | — | — |
| Jul – Dec | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|
| Days with measurable rain (days) | 0.3 | 0.5 | 1.0 | 3 | 7 | 10 |
| Days with high ≥ 32°C (days) | 0.4 | 0.7 | 2 | 0.8 | — | — |
| Days with low ≤ 0°C (days) | — | — | — | — | — | 0.3 |
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 | 82 | 80 | 78 | 74 | 74 | 73 | 70 | 69 | 76 | 82 |
| Wind speed (m/s) | 2.2 | 2.3 | 2.3 | 2.4 | 2.4 | 2.5 | 2.3 | 2.2 | 2.0 | 1.9 | 2.0 | 2.3 |
| 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 | 82 | 80 | 78 | 74 |
| Wind speed (m/s) | 2.2 | 2.3 | 2.3 | 2.4 | 2.4 | 2.5 |
| 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 (%) | 74 | 73 | 70 | 69 | 76 | 82 |
| Wind speed (m/s) | 2.3 | 2.2 | 2.0 | 1.9 | 2.0 | 2.3 |
Methodology & sources
Temperature & precipitation — the official 1991–2020 climate normals from NOAA's U.S. Climate Normals, measured at Berkeley (NOAA GHCN station USC00040693), about 29 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.