San Marcos, Texas climate: Normal weather by month, frost dates and records
San Marcos's normal year runs from 39°F January nights to 97°F August afternoons, with 36.5 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 20.3°C, January lows of 4°C, August highs of 36°C, 928 mm of precipitation a year.
- NOAA stationSan Marcos
- Station IDUSC00417983
- Location29.88°N 97.95°W
- Elevation665 ft (203 m)
- Population74,316
On October 23, the normal high in San Marcos is 80°F and the normal low 56°F, and the chance of measurable rain or snow is 20%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for San Marcos.
- Jan 62° 39°
- Feb 67° 42°
- Mar 73° 50°
- Apr 80° 56°
- May 86° 65°
- Jun 92° 72°
- Jul 96° 73°
- Aug 97° 74°
- Sep 91° 69°
- Oct 82° 58°
- Nov 72° 48°
- Dec 64° 41°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
What is the weather like in San Marcos each month?
August is the warmest month, with normal highs of 97°F; January the coldest, with normal lows of 39°F. The most precipitation falls in May (4.53 in), the least in February (1.73 in).
Each month has its own page with the day-by-day normals, the month's records and its recent years:
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 62°F | 39°F | 50.6°F | 2.41 | 7 | <1 | 7 | 10 h 30 min |
| February | 67°F | 42°F | 54.5°F | 1.73 | 7 | <1 | 4 | 11 h 10 min |
| March | 73°F | 50°F | 61.3°F | 2.76 | 8 | <1 | 1 | 12 h |
| April | 80°F | 56°F | 68.0°F | 3.20 | 7 | 2 | <1 | 12 h 50 min |
| May | 86°F | 65°F | 75.5°F | 4.53 | 8 | 10 | <1 | 13 h 40 min |
| June | 92°F | 72°F | 82.1°F | 3.57 | 6 | 24 | <1 | 14 h |
| July | 96°F | 73°F | 84.5°F | 2.21 | 5 | 29 | <1 | 13 h 50 min |
| August | 97°F | 74°F | 85.2°F | 2.60 | 5 | 29 | <1 | 13 h 20 min |
| September | 91°F | 69°F | 79.5°F | 4.03 | 7 | 19 | <1 | 12 h 20 min |
| October | 82°F | 58°F | 70.1°F | 4.41 | 6 | 5 | <1 | 11 h 30 min |
| November | 72°F | 48°F | 59.9°F | 2.69 | 6 | <1 | 2 | 10 h 40 min |
| December | 64°F | 41°F | 52.2°F | 2.41 | 8 | <1 | 6 | 10 h 10 min |
| Year (annual) | 80°F | 57°F | 68.6°F | 36.55 | 80 | 117 | 20 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | 17°C | 4°C | 10.3°C | 61 mm |
| February | 19°C | 6°C | 12.5°C | 44 mm |
| March | 23°C | 10°C | 16.3°C | 70 mm |
| April | 27°C | 13°C | 20.0°C | 81 mm |
| May | 30°C | 18°C | 24.2°C | 115 mm |
| June | 34°C | 22°C | 27.8°C | 91 mm |
| July | 35°C | 23°C | 29.2°C | 56 mm |
| August | 36°C | 23°C | 29.6°C | 66 mm |
| September | 33°C | 20°C | 26.4°C | 102 mm |
| October | 28°C | 15°C | 21.2°C | 112 mm |
| November | 22°C | 9°C | 15.5°C | 68 mm |
| December | 18°C | 5°C | 11.2°C | 61 mm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00417983; annual normals. Wet days: 0.01 inch or more; 90°F days and freezing nights: NOAA's day counts. Daylight: sunrise to sunset on the 15th, computed from the latitude.
When is the best weather to visit San Marcos?
Normal highs sit between 65°F and 85°F in February, March, April, October and November. Of those, October has the fewest days with rain (6).
That is a measurement, not a recommendation: it counts the months whose normal afternoon high sits between 65°F and 85°F, where a light layer is enough by day.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00417983.
When is the last frost in San Marcos?
In San Marcos, the last spring frost (32°F) comes after February 28 in half of years and after March 21 in one year in ten; the first autumn frost comes before November 29 in half of years and before November 8 in one year in ten.
Frost-free in half of yearsFrost in 1 to 9 years out of 10Frost most years
- Last spring frost, half of years after
- February 281 year in 10 after March 21; 9 in 10 after February 1
- First autumn frost, half of years before
- November 291 year in 10 before November 8; 9 in 10 before December 21
NOAA puts the median frost-free season at 273 days, and the season without a hard freeze (28°F) at 306 days.
A hard freeze (28°F) comes after February 13 in half of springs and before December 15 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts San Marcos in zone 9a across its 2 ZIP code areas (9a in 78666, the largest). By the map's own method, the average of each year's coldest night over 1991-2020, San Marcos's NOAA station is in zone 9a: the coldest night of a typical year reaches 23°F (15 complete years).
Frost dates for every NOAA station in Texas · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00417983; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026; the station zone: ACIS daily lows, 1991-2020. A 10% date means one year in ten has a frost after it in spring or before it in autumn.
What hardiness zone is each San Marcos ZIP code in?
The USDA's 2023 map gives each ZIP code area one zone. San Marcos's 2 ZIP code areas are all in zone 9a. Each ZIP's frost dates are in the frost tool.
Source: USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026; ZIP areas in the place: Census Bureau 2020 ZCTA-to-place relationship file. A ZIP area counts when at least a tenth of its land (and 0.5 km²) lies in the place.
How hot and how cold does it get in San Marcos?
In a normal year in San Marcos, 117 days a year reach 90°F (21 of them 100°F or more), 20 nights fall to 32°F or colder and 80 days bring measurable precipitation.
- Days at 90°F or more
- 117a normal year
- Days at 100°F or more
- 21a normal year
- Nights at 32°F or colder
- 20a normal year
- Days that stay below freezing
- fewer than 1high of 32°F or less
- Days with 0.01 inch of precipitation
- 80a normal year
The highest temperature in this station's record (since 1895) is 111°F, on August 23, 1917; the lowest is −2°F, on January 31, 1949.
The wettest calendar year on that record is 2015, with 52.29 in; the snowiest season is 1929–30, with 10.0 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00417983; records: ACIS (NOAA Regional Climate Centers), station USC00417983. Records use complete months only; a month missing more than three days is left out.
How sunny is San Marcos?
Over a year 79% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around San Marcos, 4.8 kWh per square metre a day. August is the sunniest month (87%) and February the cloudiest (68%). Among the 459 U.S. places of 50,000 or more, that ranks tied 176th (with 33 others) in sunshine.
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 72% | 3.0 |
| February | 68% | 3.5 |
| March | 71% | 4.5 |
| April | 74% | 5.3 |
| May | 78% | 5.9 |
| June | 84% | 6.7 |
| July | 86% | 6.6 |
| August | 87% | 6.3 |
| September | 81% | 5.2 |
| October | 82% | 4.4 |
| November | 76% | 3.3 |
| December | 71% | 2.7 |
Source: NASA POWER solar climatology, 2001-2020 (CERES SYN1deg). Satellite-based, for the 1-degree cell (about 100 km across) around the station, so it describes the area rather than the airport.
How much heating and cooling does San Marcos need?
A normal year in San Marcos brings 1,620 heating degree days, 70% fewer than the median U.S. place (5,373), and 2,974 cooling degree days, 3.3 times the median (908). Three months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 7,089 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 452 | 6 |
| February | 308 | 14 |
| March | 167 | 52 |
| April | 43 | 135 |
| May | 4 | 331 |
| June | 0 | 511 |
| July | 0 | 606 |
| August | 0 | 628 |
| September | 1 | 436 |
| October | 41 | 199 |
| November | 199 | 46 |
| December | 405 | 10 |
| Year (annual) | 1,620 | 2,974 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00417983. A degree day is one degree of a day's mean temperature below 65°F (heating) or above it (cooling); utilities use them to estimate energy use.
Has San Marcos been warmer than normal lately?
2025 averaged 71.3°F, 2.8°F above the 1991-2020 normal of 68.6°F. 4 of the 4 complete years since 2022 ran warmer than the normal.
| Year | Mean | Against normal | Precip. |
|---|---|---|---|
| 2022 | 68.9°F | +0.3°F | 20.42 |
| 2023 | 70.8°F | +2.3°F | 28.87 |
| 2024 | 71.1°F | +2.5°F | 37.00 |
| 2025 | 71.3°F | +2.8°F | 24.67 |
Over 53 complete years from 1909 to 2025, the station's annual mean temperature rose at a fitted 2.3°F per century (+0.13°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USC00417983; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does San Marcos's climate compare?
San Marcos is warmer than 230 of the other 320 places with their own NOAA record in Texas, and wetter than 201. Across the 7,247 U.S. stations with normals, its annual mean of 68.6°F is warmer than 94%.
In the Köppen classification computed from these normals, San Marcos is Cfa: temperate, no dry season, hot summer. What the classes mean.
Places with the most similar year elsewhere
Measured month by month on the normal high, low and precipitation, among places of 20,000 or more people in other states:
Source: NOAA NCEI 1991-2020 normals for every station PlainClimate covers. Similarity: the root-mean-square difference of the 36 monthly figures, precipitation weighted so an inch counts like 6°F.
Which places near San Marcos share this climate record?
7 places have no NOAA station with 1991-2020 normals of their own, and this station is the nearest full record. A place's own climate can differ from these figures, by several degrees where it sits much higher or lower than the station, nearer the coast, or inside a large city's heat; for the larger places the next nearest records are named with their yearly mean, so the spread around them is visible, and places of 50,000 or more have their own page with NOAA's gridded normals.
- Kyle, TXalso near: Dripping Springs (17 mi, 67.4°F a year); Canyon Lake (21 mi, 68.1°F a year)65,833 people · 9 mi NE
- Redwood, TX3,586 people · 6 mi SE
- Uhland, TX1,885 people · 11 mi NE
- Martindale, TX1,266 people · 7 mi E
- Niederwald, TX720 people · 13 mi NE
- Mountain City, TX676 people · 11 mi N
- Staples, TX190 people · 11 mi SE
Source: Census Bureau 2024 Gazetteer (place centers) and Vintage 2024 population estimates. Distance and direction from the station to each place's center.
Questions about San Marcos's climate
What is the coldest month in San Marcos?
January, with a normal high of 62°F and a normal low of 39°F. The warmest is August (97°F by day, 74°F at night).
Does it snow in San Marcos?
Rarely: NOAA's normal is no measurable snow a year.
What is the rainiest month in San Marcos?
May, with 4.53 in of precipitation in a normal year; the driest is February with 1.73 in.
What plant hardiness zone is San Marcos in?
The USDA's 2023 map puts San Marcos in zone 9a across its 2 ZIP code areas (9a in 78666, the largest). By the same method at San Marcos's NOAA station, the coldest night of a typical year reaches 23°F (15 years, 1991-2020): zone 9a.
How late can frost come in San Marcos?
In half of years the last 32°F night comes after February 28; in one year in ten it comes after March 21. Waiting until March 21 leaves about a one-in-ten chance of a later frost.
Nearby and next
- San Marcos in OctoberThis month day by day, its records and recent years
- Texas climateThe statewide normals and every place in the state
- Austin San Antonio, TX13 miles from this station, 69.6°F a year
- Canyon Lake, TX15 miles from this station, 68.1°F a year
- New Braunfels, TX20 miles from this station, 67.1°F a year
- Luling, TX22 miles from this station, 69.4°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made