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Castle Rock, Colorado climate

Cfa Humid subtropical

Castle Rock has a seasonal cool-temperate climate (Humid subtropical, Köppen Cfa). The hottest month is July with an average daily high near 87°F, while the coldest is December averaging around 19°F at night. Precipitation totals about 15 inches a year and is strongly seasonal — August alone averages 2.2 inches while December barely receives 0.35 inches.

☀️ Summers

Hot

Highs near 87°F in July.

About 31 days a year above 90 °F

❄️ Winters

Very cold

Lows near 19°F in December.

About 151 freezing nights a year

🌧️ Rain

Fairly dry

About 15 in of rain a year.

Wettest in August

⛅ Sky & trend

Partly cloudy

A roughly even mix of sun and cloud.

+0.2 °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

Castle Rock climate normals (1991–2020)

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Avg high (°F)	45	46	54	60	69	81	87	85	77	64	52	44
Avg temp (°F)	32	33	41	47	56	67	73	71	63	50	39	31
Avg low (°F)	19	20	27	34	43	52	59	57	49	36	26	19
Precipitation (in)	0.4	0.4	1.0	1.9	2.0	2.0	1.8	2.3	1.3	1.0	0.5	0.4

Jan – Jun	Jan	Feb	Mar	Apr	May	Jun
Avg high (°F)	45	46	54	60	69	81
Avg temp (°F)	32	33	41	47	56	67
Avg low (°F)	19	20	27	34	43	52
Precipitation (in)	0.4	0.4	1.0	1.9	2.0	2.0

Jul – Dec	Jul	Aug	Sep	Oct	Nov	Dec
Avg high (°F)	87	85	77	64	52	44
Avg temp (°F)	73	71	63	50	39	31
Avg low (°F)	59	57	49	36	26	19
Precipitation (in)	1.8	2.3	1.3	1.0	0.5	0.4

How often — frequency of weather events

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Days with measurable rain (days)	4	5	6	9	9	8	10	10	6	6	4	4
Days with high ≥ 90°F (days)	—	—	—	—	0.4	6	14	8	2	—	—	—
Days with low ≤ 32°F (days)	28	25	21	12	3	0.0	—	—	0.6	9	22	30
Days with snowfall ≥ 1 in (days)	0.6	0.7	0.7	0.3	0.1	—	—	—	0.0	0.5	0.6	1

Jan – Jun	Jan	Feb	Mar	Apr	May	Jun
Days with measurable rain (days)	4	5	6	9	9	8
Days with high ≥ 90°F (days)	—	—	—	—	0.4	6
Days with low ≤ 32°F (days)	28	25	21	12	3	0.0
Days with snowfall ≥ 1 in (days)	0.6	0.7	0.7	0.3	0.1	—

Jul – Dec	Jul	Aug	Sep	Oct	Nov	Dec
Days with measurable rain (days)	10	10	6	6	4	4
Days with high ≥ 90°F (days)	14	8	2	—	—	—
Days with low ≤ 32°F (days)	—	—	0.6	9	22	30
Days with snowfall ≥ 1 in (days)	—	—	0.0	0.5	0.6	1

Sky & atmosphere

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Cloud cover (%)	57	57	56	59	58	49	50	50	43	46	51	55
Clear days (≤ 30% cloud)	6	6	7	6	5	8	8	8	12	11	9	7
Partly cloudy days (30–70%)	14	13	13	12	14	15	16	14	11	11	12	14
Cloudy days (≥ 70%)	12	10	11	12	12	7	7	9	7	9	10	10
Relative humidity (%)	56	55	52	51	49	42	45	47	45	48	52	56
Wind speed (mph)	6.2	6.4	6.4	6.5	5.7	5.5	5.2	4.9	4.9	5.1	5.4	5.7

Jan – Jun	Jan	Feb	Mar	Apr	May	Jun
Cloud cover (%)	57	57	56	59	58	49
Clear days (≤ 30% cloud)	6	6	7	6	5	8
Partly cloudy days (30–70%)	14	13	13	12	14	15
Cloudy days (≥ 70%)	12	10	11	12	12	7
Relative humidity (%)	56	55	52	51	49	42
Wind speed (mph)	6.2	6.4	6.4	6.5	5.7	5.5

Jul – Dec	Jul	Aug	Sep	Oct	Nov	Dec
Cloud cover (%)	50	50	43	46	51	55
Clear days (≤ 30% cloud)	8	8	12	11	9	7
Partly cloudy days (30–70%)	16	14	11	11	12	14
Cloudy days (≥ 70%)	7	9	7	9	10	10
Relative humidity (%)	45	47	45	48	52	56
Wind speed (mph)	5.2	4.9	4.9	5.1	5.4	5.7

Methodology & sources

Temperature & precipitation — the official 1991–2020 climate normals from NOAA's U.S. Climate Normals, measured at Denver Centennial AP (NOAA GHCN station USW00093067), about 21 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 →