Frost dates for San Marcos, TX
At San Marcos, the median last spring frost (32°F) is Feb 28 and the median first fall frost is Nov 29, for a typical growing season of 273 days. For a 90% chance that the last frost has passed, wait until Mar 21. Nearby ZIP codes are in USDA hardiness zone 9a.
- Feb 28Last spring frost (median)50% chance of 32°F after this date
- Mar 21Safer planting date10% chance of 32°F after this date
- Nov 29First fall frost (median)50% chance of 32°F by this date
- 273 daysGrowing season (median)between 32°F freezes
Last spring frost dates
The chance that the temperature drops to the threshold after each date.
| Temperature | 90% chance later | 50% chance later | 10% chance later |
|---|---|---|---|
| 36°F | Feb 23 | Mar 14 | Apr 5 |
| 32°F | Feb 1 | Feb 28 | Mar 21 |
| 28°F | Jan 9 | Feb 13 | Mar 8 |
| 24°F | Dec 26 | Jan 29 | Feb 28 |
First fall frost dates
The chance that the temperature has dropped to the threshold by each date.
| Temperature | 10% chance by | 50% chance by | 90% chance by |
|---|---|---|---|
| 36°F | Nov 1 | Nov 16 | Dec 4 |
| 32°F | Nov 8 | Nov 29 | Dec 21 |
| 28°F | Nov 19 | Dec 15 | Jan 13 |
| 24°F | Dec 5 | Jan 2 | Feb 5 |
Growing season length
Days between the last spring and first fall freeze, as the length reached in 9, 5 and 1 out of 10 years.
| Temperature | 9 in 10 years at least | 5 in 10 years at least | 1 in 10 years at least |
|---|---|---|---|
| 36°F | 218 days | 246 days | 272 days |
| 32°F | 243 days | 273 days | 307 days |
| 28°F | 270 days | 306 days | 345 days |
| 24°F | 302 days | 343 days | 365 days |
Chance of a freeze in any year
| Temperature | Chance per year |
|---|---|
| 36°F | 100% |
| 32°F | 100% |
| 28°F | 98% |
| 24°F | 75% |
ZIP codes whose closest station is this one
| ZIP | Hardiness zone | Avg. extreme low | Distance |
|---|---|---|---|
| 78666 | 9a | 20 to 25°F | 3 km |
| 78655 | 9a | 20 to 25°F | 13 km |
| 78656 | 9a | 20 to 25°F | 14 km |
| 78670 | 9a | 20 to 25°F | 16 km |
| 78640 | 9a | 20 to 25°F | 18 km |
Not the official USDA Plant Hardiness Zone Map. Zones shown here are the values published in the USDA-ARS / Oregon State University PRISM Group 2023 ZIP code tables, shown unaltered. For the official interactive map, visit planthardiness.ars.usda.gov.
About this station
- NOAA station ID USC00417983, at 29.8833, -97.9494, elevation 203 m (665 ft).
- Data quality: Standard (24+ years of data), 27 years of freeze data.
- Average days per year at or below 32°F: 20.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- New Braunfels WFO (21 km)
- Austin San Antonio (21 km)
- Canyon Dam (24 km)
- New Braunfels (32 km)
- Luling (36 km)
- Dripping Springs 6 E (38 km)
- Austin Bergstrom Airport (42 km)
- Austin 6s (43 km)
Sources
- NOAA National Centers for Environmental Information, U.S. Climate Normals 1991–2020, annual/seasonal normals by station (version 1.0.1), file dated June 27, 2023; documentation.
- USDA Agricultural Research Service and PRISM Group, Oregon State University, 2023 Plant Hardiness Zone Map ZIP code tables (CONUS, Alaska, Hawaii, Puerto Rico), files dated November 17, 2023. Data © PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed November 1, 2026. Official map: planthardiness.ars.usda.gov.
- U.S. Census Bureau, 2024 Gazetteer ZIP Code Tabulation Areas file, dated August 30, 2024 (ZIP centroids used to find the nearest station).
Freeze dates are 30-year probabilities, not forecasts. Check your local forecast before planting tender plants.