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Santa Rosa, California climate

Csb Warm-summer Mediterranean

Santa Rosa has a mildly seasonal mild-temperate climate (Warm-summer Mediterranean, Köppen Csb). The hottest month is August with an average daily high near 28°C, while the coldest is December averaging around 3°C at night. Precipitation totals about 801 mm a year and is strongly seasonal — December alone averages 164 mm while July barely receives 0 mm.

☀️ Summers

Warm

Highs near 28°C in August.

About 23 days a year above 32 °C

❄️ Winters

Chilly

Lows near 3°C in December.

About 14 freezing nights a year

🌧️ Rain

Moderate rainfall

About 801 mm of rain a year.

Wettest in December

⛅ Sky & trend

Fairly sunny

More sun than cloud through the year.

+0.3 °C vs 50 years ago

Temperature & precipitation

Daily high–low temperature range with the monthly average, plus monthly precipitation · 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

Santa Rosa climate normals (1991–2020)

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Avg high (°C)	15	18	19	21	24	27	28	28	29	26	20	15
Avg temp (°C)	10	11	12	14	16	19	19	20	20	17	13	9
Avg low (°C)	4	4	6	7	9	11	11	11	11	9	6	3
Precipitation (mm)	147	162	108	50	33	7	0	1	4	41	83	164

Jan – Jun	Jan	Feb	Mar	Apr	May	Jun
Avg high (°C)	15	18	19	21	24	27
Avg temp (°C)	10	11	12	14	16	19
Avg low (°C)	4	4	6	7	9	11
Precipitation (mm)	147	162	108	50	33	7

Jul – Dec	Jul	Aug	Sep	Oct	Nov	Dec
Avg high (°C)	28	28	29	26	20	15
Avg temp (°C)	19	20	20	17	13	9
Avg low (°C)	11	11	11	9	6	3
Precipitation (mm)	0	1	4	41	83	164

How often — frequency of weather events

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Days with measurable rain (days)	13	12	11	7	5	1	0.3	0.4	1	4	9	12
Days with high ≥ 32°C (days)	—	—	0.0	0.3	0.7	4	4	6	7	2	—	—
Days with low ≤ 0°C (days)	4	2	0.5	0.0	0.0	—	—	0.0	—	—	2	5

Jan – Jun	Jan	Feb	Mar	Apr	May	Jun
Days with measurable rain (days)	13	12	11	7	5	1
Days with high ≥ 32°C (days)	—	—	0.0	0.3	0.7	4
Days with low ≤ 0°C (days)	4	2	0.5	0.0	0.0	—

Jul – Dec	Jul	Aug	Sep	Oct	Nov	Dec
Days with measurable rain (days)	0.3	0.4	1	4	9	12
Days with high ≥ 32°C (days)	4	6	7	2	—	—
Days with low ≤ 0°C (days)	—	0.0	—	—	2	5

Sky & atmosphere

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Cloud cover (%)	59	57	54	48	41	30	26	26	26	35	47	58
Clear days (≤ 30% cloud)	8	8	10	11	14	19	21	22	20	18	12	8
Partly cloudy days (30–70%)	9	8	9	9	10	7	8	7	8	8	9	9
Cloudy days (≥ 70%)	15	12	13	10	7	4	2	2	2	6	10	14
Relative humidity (%)	84	83	81	77	70	57	49	48	47	54	71	81
Wind speed (km/h)	5.4	5.7	5.7	6.0	6.3	6.6	6.6	6.3	5.8	5.6	5.2	5.7

Jan – Jun	Jan	Feb	Mar	Apr	May	Jun
Cloud cover (%)	59	57	54	48	41	30
Clear days (≤ 30% cloud)	8	8	10	11	14	19
Partly cloudy days (30–70%)	9	8	9	9	10	7
Cloudy days (≥ 70%)	15	12	13	10	7	4
Relative humidity (%)	84	83	81	77	70	57
Wind speed (km/h)	5.4	5.7	5.7	6.0	6.3	6.6

Jul – Dec	Jul	Aug	Sep	Oct	Nov	Dec
Cloud cover (%)	26	26	26	35	47	58
Clear days (≤ 30% cloud)	21	22	20	18	12	8
Partly cloudy days (30–70%)	8	7	8	8	9	9
Cloudy days (≥ 70%)	2	2	2	6	10	14
Relative humidity (%)	49	48	47	54	71	81
Wind speed (km/h)	6.6	6.3	5.8	5.6	5.2	5.7

Methodology & sources

Temperature & precipitation — the official 1991–2020 climate normals from NOAA's U.S. Climate Normals, measured at Santa Rosa (NOAA GHCN station USC00047965), about 2 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 →