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Mount Vernon, Washington climate
Csb Warm-summer Mediterranean
Mount Vernon has a mildly seasonal cool-temperate climate (Warm-summer Mediterranean, Köppen Csb). The hottest month is August with an average daily high near 21°C, while the coldest is December averaging around 3°C at night. Precipitation totals about 506 mm a year and is strongly seasonal — November alone averages 80 mm while July barely receives 16 mm. Snow is occasional (14 cm of snow per year on average).
Temperature & precipitation
Daily high–low temperature range with the monthly average, plus monthly precipitation split into rain and snow · 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 countsMount Vernon climate normals (1991–2020)
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high (°C) | 10 | 11 | 13 | 15 | 17 | 19 | 21 | 21 | 19 | 16 | 12 | 9 |
| Avg temp (°C) | 7 | 7 | 9 | 11 | 13 | 15 | 16 | 17 | 15 | 12 | 8 | 6 |
| Avg low (°C) | 3 | 3 | 5 | 6 | 9 | 11 | 12 | 12 | 10 | 8 | 5 | 3 |
| Precipitation (mm) | 62 | 41 | 43 | 43 | 43 | 28 | 16 | 22 | 27 | 52 | 80 | 50 |
| Snowfall (cm) | 3 | 3 | 2 | — | — | — | — | — | — | — | 1 | 6 |
| Jan – Jun | Jan | Feb | Mar | Apr | May | Jun |
|---|---|---|---|---|---|---|
| Avg high (°C) | 10 | 11 | 13 | 15 | 17 | 19 |
| Avg temp (°C) | 7 | 7 | 9 | 11 | 13 | 15 |
| Avg low (°C) | 3 | 3 | 5 | 6 | 9 | 11 |
| Precipitation (mm) | 62 | 41 | 43 | 43 | 43 | 28 |
| Snowfall (cm) | 3 | 3 | 2 | — | — | — |
| Jul – Dec | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|
| Avg high (°C) | 21 | 21 | 19 | 16 | 12 | 9 |
| Avg temp (°C) | 16 | 17 | 15 | 12 | 8 | 6 |
| Avg low (°C) | 12 | 12 | 10 | 8 | 5 | 3 |
| Precipitation (mm) | 16 | 22 | 27 | 52 | 80 | 50 |
| Snowfall (cm) | — | — | — | — | 1 | 6 |
How often — frequency of weather events
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Days with measurable rain (days) | 15 | 13 | 14 | 12 | 10 | 8 | 5 | 5 | 9 | 13 | 15 | 14 |
| Days with low ≤ 0°C (days) | 9 | 9 | 4 | 0.9 | 0.1 | — | — | 0.0 | — | 0.9 | 4 | 8 |
| Days with snowfall ≥ 2.5 cm (days) | 0.3 | 0.1 | 0.1 | — | — | — | — | — | — | — | 0.0 | 0.2 |
| Jan – Jun | Jan | Feb | Mar | Apr | May | Jun |
|---|---|---|---|---|---|---|
| Days with measurable rain (days) | 15 | 13 | 14 | 12 | 10 | 8 |
| Days with low ≤ 0°C (days) | 9 | 9 | 4 | 0.9 | 0.1 | — |
| Days with snowfall ≥ 2.5 cm (days) | 0.3 | 0.1 | 0.1 | — | — | — |
| Jul – Dec | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|
| Days with measurable rain (days) | 5 | 5 | 9 | 13 | 15 | 14 |
| Days with low ≤ 0°C (days) | — | 0.0 | — | 0.9 | 4 | 8 |
| Days with snowfall ≥ 2.5 cm (days) | — | — | — | — | 0.0 | 0.2 |
Sky & atmosphere
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Cloud cover (%) | 79 | 74 | 76 | 73 | 68 | 66 | 48 | 49 | 53 | 69 | 77 | 80 |
| Clear days (≤ 30% cloud) | 2 | 3 | 2 | 3 | 4 | 5 | 12 | 11 | 10 | 5 | 2 | 2 |
| Partly cloudy days (30–70%) | 5 | 6 | 7 | 8 | 9 | 9 | 9 | 10 | 8 | 8 | 6 | 6 |
| Cloudy days (≥ 70%) | 23 | 19 | 22 | 19 | 18 | 16 | 10 | 10 | 12 | 18 | 21 | 23 |
| Relative humidity (%) | 90 | 86 | 84 | 81 | 80 | 80 | 79 | 78 | 79 | 85 | 89 | 89 |
| Wind speed (km/h) | 4.5 | 4.1 | 3.7 | 3.1 | 2.3 | 2.1 | 1.9 | 1.9 | 2.3 | 3.3 | 4.4 | 4.8 |
| Jan – Jun | Jan | Feb | Mar | Apr | May | Jun |
|---|---|---|---|---|---|---|
| Cloud cover (%) | 79 | 74 | 76 | 73 | 68 | 66 |
| Clear days (≤ 30% cloud) | 2 | 3 | 2 | 3 | 4 | 5 |
| Partly cloudy days (30–70%) | 5 | 6 | 7 | 8 | 9 | 9 |
| Cloudy days (≥ 70%) | 23 | 19 | 22 | 19 | 18 | 16 |
| Relative humidity (%) | 90 | 86 | 84 | 81 | 80 | 80 |
| Wind speed (km/h) | 4.5 | 4.1 | 3.7 | 3.1 | 2.3 | 2.1 |
| Jul – Dec | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|
| Cloud cover (%) | 48 | 49 | 53 | 69 | 77 | 80 |
| Clear days (≤ 30% cloud) | 12 | 11 | 10 | 5 | 2 | 2 |
| Partly cloudy days (30–70%) | 9 | 10 | 8 | 8 | 6 | 6 |
| Cloudy days (≥ 70%) | 10 | 10 | 12 | 18 | 21 | 23 |
| Relative humidity (%) | 79 | 78 | 79 | 85 | 89 | 89 |
| Wind speed (km/h) | 1.9 | 1.9 | 2.3 | 3.3 | 4.4 | 4.8 |
Methodology & sources
Temperature & precipitation — the official 1991–2020 climate normals from NOAA's U.S. Climate Normals, measured at Whidbey Island Nas (NOAA GHCN station USW00024255), about 26 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.