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Eureka, California climate
Csb Warm-summer Mediterranean
Eureka has a mildly seasonal cool-temperate climate (Warm-summer Mediterranean, Köppen Csb). The hottest month is August with an average daily high near 18°C, while the coldest is December averaging around 4°C at night. Precipitation totals about 1026 mm a year and is strongly seasonal — December alone averages 206 mm while July barely receives 5 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 countsEureka climate normals (1991–2020)
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high (°C) | 13 | 13 | 13 | 14 | 15 | 17 | 17 | 18 | 18 | 17 | 14 | 13 |
| Avg temp (°C) | 9 | 9 | 10 | 10 | 12 | 13 | 14 | 15 | 14 | 12 | 10 | 9 |
| Avg low (°C) | 5 | 5 | 6 | 7 | 9 | 10 | 11 | 12 | 10 | 8 | 6 | 4 |
| Precipitation (mm) | 169 | 143 | 146 | 92 | 42 | 18 | 5 | 5 | 17 | 59 | 124 | 206 |
| Jan – Jun | Jan | Feb | Mar | Apr | May | Jun |
|---|---|---|---|---|---|---|
| Avg high (°C) | 13 | 13 | 13 | 14 | 15 | 17 |
| Avg temp (°C) | 9 | 9 | 10 | 10 | 12 | 13 |
| Avg low (°C) | 5 | 5 | 6 | 7 | 9 | 10 |
| Precipitation (mm) | 169 | 143 | 146 | 92 | 42 | 18 |
| Jul – Dec | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|
| Avg high (°C) | 17 | 18 | 18 | 17 | 14 | 13 |
| Avg temp (°C) | 14 | 15 | 14 | 12 | 10 | 9 |
| Avg low (°C) | 11 | 12 | 10 | 8 | 6 | 4 |
| Precipitation (mm) | 5 | 5 | 17 | 59 | 124 | 206 |
How often — frequency of weather events
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Days with measurable rain (days) | 17 | 15 | 16 | 14 | 9 | 6 | 3 | 4 | 5 | 9 | 14 | 17 |
| Days with low ≤ 0°C (days) | 2 | 1 | 0.6 | 0.1 | — | — | — | — | — | — | 0.9 | 3 |
| Jan – Jun | Jan | Feb | Mar | Apr | May | Jun |
|---|---|---|---|---|---|---|
| Days with measurable rain (days) | 17 | 15 | 16 | 14 | 9 | 6 |
| Days with low ≤ 0°C (days) | 2 | 1 | 0.6 | 0.1 | — | — |
| Jul – Dec | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|
| Days with measurable rain (days) | 3 | 4 | 5 | 9 | 14 | 17 |
| Days with low ≤ 0°C (days) | — | — | — | — | 0.9 | 3 |
Sky & atmosphere
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Cloud cover (%) | 74 | 75 | 75 | 72 | 68 | 60 | 59 | 60 | 57 | 59 | 68 | 73 |
| Clear days (≤ 30% cloud) | 3 | 3 | 2 | 3 | 4 | 5 | 5 | 6 | 6 | 6 | 4 | 4 |
| Partly cloudy days (30–70%) | 7 | 6 | 8 | 8 | 10 | 12 | 13 | 12 | 13 | 12 | 9 | 7 |
| Cloudy days (≥ 70%) | 21 | 19 | 21 | 19 | 17 | 12 | 12 | 14 | 11 | 13 | 17 | 20 |
| Relative humidity (%) | 83 | 83 | 84 | 85 | 88 | 89 | 89 | 88 | 84 | 83 | 83 | 82 |
| Wind speed (km/h) | 15.6 | 15.8 | 16.0 | 15.1 | 15.3 | 16.5 | 15.0 | 13.4 | 12.3 | 12.6 | 13.9 | 16.6 |
| Jan – Jun | Jan | Feb | Mar | Apr | May | Jun |
|---|---|---|---|---|---|---|
| Cloud cover (%) | 74 | 75 | 75 | 72 | 68 | 60 |
| Clear days (≤ 30% cloud) | 3 | 3 | 2 | 3 | 4 | 5 |
| Partly cloudy days (30–70%) | 7 | 6 | 8 | 8 | 10 | 12 |
| Cloudy days (≥ 70%) | 21 | 19 | 21 | 19 | 17 | 12 |
| Relative humidity (%) | 83 | 83 | 84 | 85 | 88 | 89 |
| Wind speed (km/h) | 15.6 | 15.8 | 16.0 | 15.1 | 15.3 | 16.5 |
| Jul – Dec | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|
| Cloud cover (%) | 59 | 60 | 57 | 59 | 68 | 73 |
| Clear days (≤ 30% cloud) | 5 | 6 | 6 | 6 | 4 | 4 |
| Partly cloudy days (30–70%) | 13 | 12 | 13 | 12 | 9 | 7 |
| Cloudy days (≥ 70%) | 12 | 14 | 11 | 13 | 17 | 20 |
| Relative humidity (%) | 89 | 88 | 84 | 83 | 83 | 82 |
| Wind speed (km/h) | 15.0 | 13.4 | 12.3 | 12.6 | 13.9 | 16.6 |
Methodology & sources
Temperature & precipitation — the official 1991–2020 climate normals from NOAA's U.S. Climate Normals, measured at Eureka Wfo Woodley IS (NOAA GHCN station USW00024213), inside the city.
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.