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San Marcos, Texas climate

Cfa Humid subtropical

San Marcos has a seasonal warm-temperate climate (Humid subtropical, Köppen Cfa). The hottest month is August with an average daily high near 97°F, while the coldest is January averaging around 39°F at night. Around 37 inches of precipitation falls each year, peaking in May (4.5 inches) and easing off in February (1.7 inches).

☀️ Summers

Very hot

Highs near 97°F in August.

About 113 days a year above 90 °F

❄️ Winters

Chilly

Lows near 39°F in January.

About 18 freezing nights a year

🌧️ Rain

Moderate rainfall

About 37 in of rain a year.

Wettest in May

⛅ Sky & trend

Partly cloudy

A roughly even mix of sun and cloud.

+0.7 °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

San Marcos climate normals (1991–2020)

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Avg high (°F)	62	67	73	80	86	92	96	97	91	82	72	64
Avg temp (°F)	51	55	61	68	76	82	85	85	80	70	60	52
Avg low (°F)	39	42	50	56	65	72	73	74	69	58	48	41
Precipitation (in)	2.4	1.7	2.8	3.2	4.5	3.6	2.2	2.6	4.0	4.4	2.7	2.4

Jan – Jun	Jan	Feb	Mar	Apr	May	Jun
Avg high (°F)	62	67	73	80	86	92
Avg temp (°F)	51	55	61	68	76	82
Avg low (°F)	39	42	50	56	65	72
Precipitation (in)	2.4	1.7	2.8	3.2	4.5	3.6

Jul – Dec	Jul	Aug	Sep	Oct	Nov	Dec
Avg high (°F)	96	97	91	82	72	64
Avg temp (°F)	85	85	80	70	60	52
Avg low (°F)	73	74	69	58	48	41
Precipitation (in)	2.2	2.6	4.0	4.4	2.7	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)	7	7	8	7	7	6	5	5	7	6	6	8
Days with high ≥ 90°F (days)	—	0.2	0.3	2	9	23	28	29	18	5	0.0	—
Days with low ≤ 32°F (days)	6	4	1	—	—	0.0	—	—	—	0.0	2	5
Days with snowfall ≥ 1 in (days)	—	0.0	—	—	—	—	—	—	—	—	—	0.0

Jan – Jun	Jan	Feb	Mar	Apr	May	Jun
Days with measurable rain (days)	7	7	8	7	7	6
Days with high ≥ 90°F (days)	—	0.2	0.3	2	9	23
Days with low ≤ 32°F (days)	6	4	1	—	—	0.0
Days with snowfall ≥ 1 in (days)	—	0.0	—	—	—	—

Jul – Dec	Jul	Aug	Sep	Oct	Nov	Dec
Days with measurable rain (days)	5	5	7	6	6	8
Days with high ≥ 90°F (days)	28	29	18	5	0.0	—
Days with low ≤ 32°F (days)	—	—	—	0.0	2	5
Days with snowfall ≥ 1 in (days)	—	—	—	—	—	0.0

Sky & atmosphere

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Cloud cover (%)	60	63	63	60	59	48	43	43	47	43	53	60
Clear days (≤ 30% cloud)	7	6	6	7	6	10	13	12	11	13	9	7
Partly cloudy days (30–70%)	9	7	9	10	12	13	13	13	11	11	10	9
Cloudy days (≥ 70%)	15	15	16	14	13	8	6	6	8	8	11	15
Relative humidity (%)	72	72	71	68	70	68	63	61	67	68	71	72
Wind speed (mph)	6.6	6.9	7.2	7.4	7.1	6.6	6.6	6.0	5.5	6.1	6.4	6.4

Jan – Jun	Jan	Feb	Mar	Apr	May	Jun
Cloud cover (%)	60	63	63	60	59	48
Clear days (≤ 30% cloud)	7	6	6	7	6	10
Partly cloudy days (30–70%)	9	7	9	10	12	13
Cloudy days (≥ 70%)	15	15	16	14	13	8
Relative humidity (%)	72	72	71	68	70	68
Wind speed (mph)	6.6	6.9	7.2	7.4	7.1	6.6

Jul – Dec	Jul	Aug	Sep	Oct	Nov	Dec
Cloud cover (%)	43	43	47	43	53	60
Clear days (≤ 30% cloud)	13	12	11	13	9	7
Partly cloudy days (30–70%)	13	13	11	11	10	9
Cloudy days (≥ 70%)	6	6	8	8	11	15
Relative humidity (%)	63	61	67	68	71	72
Wind speed (mph)	6.6	6.0	5.5	6.1	6.4	6.4

Methodology & sources

Temperature & precipitation — the official 1991–2020 climate normals from NOAA's U.S. Climate Normals, measured at San Marcos (NOAA GHCN station USC00417983), inside the city.

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 →