San Marcos climate — normals and trends
San Marcos (United States) has a humid subtropical climate (Cfa) under the Köppen-Geiger classification. Its mean annual temperature is 19.7 °C and it receives 841 mm of precipitation per year.
These figures are normals computed over 86 complete calendar years, from 1940 to 2025, using ERA5 reanalysis data from the Copernicus programme.
The warmest month is August (28.5 °C on average) and the coldest is January (9.7 °C). Rainfall peaks in May.
San Marcos averages 12 frost days, 124 hot days (≥ 30 °C) and 102 rainy days per year.
San Marcos has warmed by +1.7 °C between 1940 and 2025, or +0.20 °C per decade. This trend is statistically significant.
The hottest day of the period reached 42.2 °C (on 28 August 2011) and the coldest -15.9 °C (on 31 January 1949).
Data from ERA5 reanalysis (Copernicus Climate Change Service), redistributed under a CC-BY 4.0 licence. Normals are recomputed whenever the archive is updated.
Climate normals · ERA5
San MarcosTexas
- coords
- 29.88°, -97.94°
- period
- 1940–2025 · 86 yrs
Mean daily temperature
19.7°C
Average daily high
25.3°C
Average daily low
14.8°C
Annual rainfall
841mm
Sunshine / day
9.3h
Mean relative humidity
69%
Average peak wind
17.8km/h
Seasonal range
18.8°C
Frost days (< 0 °C)
12 d/yr
Hot days (≥ 30 °C)
124 d/yr
Rainy days (≥ 1 mm)
102 d/yr
Annual snowfall
1.3 cm
Average feels-like high
25.6 °C
Average feels-like low
14.4 °C
Average peak gust
37.6 km/h
Tropical nights (≥ 20 °C)
132 d/yr
Solar radiation
17.1 MJ/m²
Has the climate changed?
One stripe per year, 1940 to 2025
+1.7 °C
since 1940
+0.2 °C per decade · r² = 0.36 · p = < 0.001
Trend fitted by linear regression (ordinary least squares) on annual means. A trend is shown only when it is statistically significant (p < 0.05).
A climograph overlays rainfall (bars) and temperature (line): the standard reading in climatology, where you can see at a glance whether the warm season is also the dry one.
Records for the period
Hottest day
42.2 °C
28 August 2011
Coldest day
-15.9 °C
31 January 1949
Wettest day
130 mm
26 August 2017
Windiest day
57.5 km/h
11 September 1961
Strongest gust
116.6 km/h
11 September 1961
Hottest feels-like
44.6 °C
10 July 2022
Coldest feels-like
-21.0 °C
23 December 1989
Snowiest day
9.9 cm
30 January 1949
Sunniest day
13.2 h
2 July 2024
Normals computed over complete calendar years 1940–2025.
A specific year
Pick a year and see how it compares to normal — warmer, drier or more extreme than usual?
Across the whole year
Month by month
| High | vs. normal | Precipitation | vs. normal | |
|---|---|---|---|---|
| Jan | 13.2 °C | -2.1 °C | 64 mm | +8 mm |
| Feb | 18.1 °C | +0.6 °C | 44 mm | -19 mm |
| Mar | 26.8 °C | +5.2 °C | 61 mm | -8 mm |
| Apr | 28.2 °C | +2.8 °C | 67 mm | -29 mm |
| May | 31.3 °C | +2.6 °C | 124 mm | +5 mm |
| Jun | 33.2 °C | +1.2 °C | 78 mm | +5 mm |
| Jul | 32.4 °C | -1.5 °C | 213 mm | +167 mm |
| Aug | 35.5 °C | +1.2 °C | 25 mm | -26 mm |
| Sep | 33.8 °C | +2.7 °C | 29 mm | -44 mm |
| Oct | 30.9 °C | +4.3 °C | 32 mm | -42 mm |
| Nov | 24.9 °C | +4.3 °C | 34 mm | -30 mm |
| Dec | 19.7 °C | +2.9 °C | 15 mm | -41 mm |
The year's extremes
What was the weather like that day?
Your birthday, a wedding, a memorable trip: discover the actual weather for any date since 1940.
Frequently asked questions
What is the climate of San Marcos?
San Marcos has a humid subtropical climate (Köppen Cfa). Over 1940-2025, the average annual temperature is 19.7 °C and it receives 841 mm of precipitation per year.
What is the hottest day ever recorded in San Marcos?
The hottest day measured in San Marcos between 1940 and 2025 was 28 August 2011, reaching 42.2 °C.
What is the coldest day in San Marcos?
The coldest day measured in San Marcos between 1940 and 2025 was 31 January 1949, at -15.9 °C.
Does it snow in San Marcos?
Yes. San Marcos gets on average 1.3 cm of snow per year and has around 12 frost days.
Has the climate of San Marcos warmed?
Yes: San Marcos warmed by +1.7 °C between 1940 and 2025, a statistically significant trend.
What is the wettest day in San Marcos?
The wettest day measured in San Marcos between 1940 and 2025 was 26 August 2017, with 130 mm of rain in 24 hours.
What was the windiest day in San Marcos?
The windiest day measured in San Marcos between 1940 and 2025 was 11 September 1961, with winds reaching 57.5 km/h.
What is the warmest month in San Marcos?
The warmest month in San Marcos is August (28.5 °C on average); the coldest is January (9.7 °C).
How much does it rain in San Marcos?
San Marcos receives on average 841 mm of precipitation per year, spread over about 102 rainy days.
Is it sunny in San Marcos?
San Marcos gets on average 9.3 hours of sunshine per day, roughly 3,395 hours per year over 1940-2025.
What is the biggest single-day snowfall in San Marcos?
The heaviest 24-hour snowfall measured in San Marcos between 1940 and 2025 was 30 January 1949, with 9.9 cm.
Are there tropical nights in San Marcos?
Yes: San Marcos has on average 132 tropical nights per year (temperature staying above 20 °C), over 1940-2025.
What was the most extreme apparent temperature in San Marcos?
In San Marcos, between 1940 and 2025, the highest apparent temperature reached 44.6 °C on 10 July 2022, and the lowest was -21.0 °C on 23 December 1989.
Compare San Marcos with another city
Pick a second city: its normals will be set against these, indicator by indicator.
Nearby cities
The climate around San Marcos