Frost dates / Texas / San Marcos
Frost dates in San Marcos, TX
The station on this page is SAN MARCOS, TX US (USC00417983), 1 miles from the city point. Population in the Census 2024 estimate is 74,316.
Zone 9aUSDA average annual extreme minimum 20°F to 25°F, from ZIP 78666 (2.9 miles from the city point used on this page).
Outside the median season Growing seasonTicks: 10%, 50%, and 90%
Last 32°F in spring
NCEI’s probability is the chance the last spring minimum of 32°F or lower occurs on or after the date.
| Probability | Date | How to read it |
|---|---|---|
| 90% | February 1 | Earlier date. A last 32°F on or after this day is common. |
| 50% | February 28 | Median. |
| 10% | March 21 | Later date. A last 32°F on or after this day is uncommon. |
First 32°F in fall
NCEI’s probability is the chance the first autumn minimum of 32°F or lower occurs on or before the date.
| Probability | Date | How to read it |
|---|---|---|
| 10% | November 8 | Earlier date. A first 32°F on or before this day is uncommon. |
| 50% | November 29 | Median. |
| 90% | December 21 | Later date. A first 32°F on or before this day is common. |
32°F growing-season length
Days between the last spring 32°F and the first autumn 32°F. The figure is a length the season meets or exceeds at that probability, from NCEI, not a subtraction done on this site.
| Probability the season is at least this long | Days |
|---|---|
| 10% | 307 |
| 50% | 273 |
| 90% | 243 |
28°F threshold
| 10% | 50% | 90% | |
|---|---|---|---|
| Last, on or after | March 8 | February 13 | January 9 |
| First, on or before | November 19 | December 15 | January 13 |
| Season at least | 345 days | 306 days | 270 days |
36°F threshold
| 10% | 50% | 90% | |
|---|---|---|---|
| Last, on or after | April 5 | March 14 | February 23 |
| First, on or before | November 1 | November 16 | December 4 |
| Season at least | 272 days | 246 days | 218 days |
Station SAN MARCOS, TX US (USC00417983). Completeness flag S, 27 years used for the 32°F dates. NCEI’s annual probability of at least one day at or below 32°F is 100%. Freeze dates are conditional on that threshold occurring. Elevation 202.7 m. The same probability language applies to the 28°F and 36°F rows when those dates passed the same quality checks.
Planting calendar for San Marcos · Zone 9a
Check a crop against this station
San Marcos, TX
Zone 9aAverage annual extreme minimum 20°F to 25°F
Outside the median season Growing seasonTicks: 10%, 50%, and 90%
Texas. Nearest qualified station: SAN MARCOS, TX US (USC00417983), 1 miles. Median last 32°F February 28. Median first 32°F November 29. The 50% growing-season length is 273 days.
Open the ZIP page · Crop guides for Texas
32°F probabilities at this station
| 10% | 50% | 90% | |
|---|---|---|---|
| Last 32°F on or after | March 21 | February 28 | February 1 |
| First 32°F on or before | November 8 | November 29 | December 21 |
Column order matches the NCEI file: for the last freeze, 10% is the later date and 90% is the earlier date. How to read the probabilities.
Planting calendar
Windows below are from Texas A&M AgriLife Extension, Texas Home Vegetable Gardening Guide, retrieved 2026-10-10. Table 8 is statewide and is written as weeks before or after the frost-free date (spring) and the first freeze date (fall). It is not a single calendar date for every Texas city.
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