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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 70°F, while the coldest is December averaging around 38°F at night. Precipitation totals about 20 inches a year and is strongly seasonal — November alone averages 3.1 inches while July barely receives 0.63 inches. Snow is occasional (5 inches of snow per year on average).

☀️ Summers

Mild

Highs near 70°F in August.

❄️ Winters

Chilly

Lows near 38°F in December.

About 36 freezing nights a year

🌧️ Rain & snow

Fairly dry

About 20 in of rain a year, plus 5 in of snow.

Snow falls through the winter months

⛅ Sky & trend

Often cloudy

Cloudy skies much of the year.

+2.2 °F vs 50 years ago

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 figures

Clear vs cloudy days

Share of days each month that are clear, partly cloudy or cloudy · 1991–2020 · hover a month for the day counts

Mount Vernon climate normals (1991–2020)

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Avg high (°F)	49	51	55	58	62	66	69	70	67	60	54	49
Avg temp (°F)	44	44	47	51	55	59	62	62	59	53	47	43
Avg low (°F)	38	37	40	43	48	52	54	54	50	46	41	38
Precipitation (in)	2.4	1.6	1.7	1.7	1.7	1.1	0.6	0.9	1.1	2.0	3.1	2.0
Snowfall (in)	1.1	1.0	0.6	—	—	—	—	—	—	—	0.3	2.4

Jan – Jun	Jan	Feb	Mar	Apr	May	Jun
Avg high (°F)	49	51	55	58	62	66
Avg temp (°F)	44	44	47	51	55	59
Avg low (°F)	38	37	40	43	48	52
Precipitation (in)	2.4	1.6	1.7	1.7	1.7	1.1
Snowfall (in)	1.1	1.0	0.6	—	—	—

Jul – Dec	Jul	Aug	Sep	Oct	Nov	Dec
Avg high (°F)	69	70	67	60	54	49
Avg temp (°F)	62	62	59	53	47	43
Avg low (°F)	54	54	50	46	41	38
Precipitation (in)	0.6	0.9	1.1	2.0	3.1	2.0
Snowfall (in)	—	—	—	—	0.3	2.4

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 ≤ 32°F (days)	9	9	4	0.9	0.1	—	—	0.0	—	0.9	4	8
Days with snowfall ≥ 1 in (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 ≤ 32°F (days)	9	9	4	0.9	0.1	—
Days with snowfall ≥ 1 in (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 ≤ 32°F (days)	—	0.0	—	0.9	4	8
Days with snowfall ≥ 1 in (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 (mph)	2.8	2.6	2.3	1.9	1.5	1.3	1.2	1.2	1.4	2.0	2.7	3.0

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 (mph)	2.8	2.6	2.3	1.9	1.5	1.3

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 (mph)	1.2	1.2	1.4	2.0	2.7	3.0

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.

How we build these numbers →