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Petaluma, California climate

Csb Warm-summer Mediterranean

Petaluma has a mildly seasonal mild-temperate climate (Warm-summer Mediterranean, Köppen Csb). The hottest month is August with an average daily high near 83°F, while the coldest is December averaging around 38°F at night. Precipitation totals about 32 inches a year and is strongly seasonal — December alone averages 6.5 inches while July barely receives 0.01 inches.

☀️ Summers

Warm

Highs near 83°F in August.

About 23 days a year above 90 °F

❄️ Winters

Chilly

Lows near 38°F in December.

About 14 freezing nights a year

🌧️ Rain

Moderate rainfall

About 32 in of rain a year.

Wettest in December

⛅ Sky & trend

Fairly sunny

More sun than cloud through the year.

+0.5 °F 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

Petaluma climate normals (1991–2020)

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Avg high (°F)	60	64	67	71	75	80	82	83	84	79	67	59
Avg temp (°F)	49	52	54	57	61	66	67	68	68	63	55	49
Avg low (°F)	38	40	42	44	48	51	52	53	51	48	42	38
Precipitation (in)	5.8	6.4	4.3	2.0	1.3	0.3	0.0	0.0	0.2	1.6	3.3	6.5

Jan – Jun	Jan	Feb	Mar	Apr	May	Jun
Avg high (°F)	60	64	67	71	75	80
Avg temp (°F)	49	52	54	57	61	66
Avg low (°F)	38	40	42	44	48	51
Precipitation (in)	5.8	6.4	4.3	2.0	1.3	0.3

Jul – Dec	Jul	Aug	Sep	Oct	Nov	Dec
Avg high (°F)	82	83	84	79	67	59
Avg temp (°F)	67	68	68	63	55	49
Avg low (°F)	52	53	51	48	42	38
Precipitation (in)	0.0	0.0	0.2	1.6	3.3	6.5

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 ≥ 90°F (days)	—	—	0.0	0.3	0.7	4	4	6	7	2	—	—
Days with low ≤ 32°F (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 ≥ 90°F (days)	—	—	0.0	0.3	0.7	4
Days with low ≤ 32°F (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 ≥ 90°F (days)	4	6	7	2	—	—
Days with low ≤ 32°F (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 (mph)	3.3	3.5	3.5	3.8	3.9	4.1	4.1	3.9	3.6	3.5	3.2	3.5

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 (mph)	3.3	3.5	3.5	3.8	3.9	4.1

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 (mph)	4.1	3.9	3.6	3.5	3.2	3.5

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 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 →