Frost dates by ZIP code: The nearest NOAA stations to your ZIP, 1991-2020 normals
Enter a five-digit ZIP code. PlainClimate finds its center (Census Bureau 2024) and the five nearest NOAA stations with frost dates, and shows each station's last spring and first autumn 32°F dates with its distance and elevation.
Frost dates near ZIP 78240
The USDA's 2023 Plant Hardiness Zone Map puts ZIP 78240 in zone 9a (the coldest night of a typical year: 20 to 25°F).
The nearest station, San Antonio, TX, is 7 miles from the ZIP's center: its last spring frost comes after February 26 in half of years and after March 17 in one year in ten. By the USDA's method its plant hardiness zone is 9a.
| Station | Distance | Elevation | Last frost (median) | 1 in 10 after | First frost (median) | Hardiness zone |
|---|---|---|---|---|---|---|
| San Antonio, TXSan Antonio International Airport | 7 mi | 789 ft | February 26 | March 17 | November 28 | 9a |
| San Antonio/Seaworld, TX | 8 mi | 940 ft | February 18 | March 16 | December 9 | – |
| San Antonio Incarnate Word, TX | 9 mi | 700 ft | February 25 | March 19 | November 28 | 9a |
| San Antonio Kelly Air Force Base, TX | 10 mi | 682 ft | February 22 | March 12 | December 2 | – |
| San Antonio Stinson Airport, TX | 15 mi | 571 ft | February 20 | March 13 | December 3 | 9a |
Frost comes later in spring at higher and colder stations and earlier in low, open ground: prefer a station at a similar elevation to yours. Hardiness zone in the table: the USDA's rule (the average of each year's coldest night, 1991-2020) applied to the station's own record.
Every frost threshold at San Antonio
NOAA publishes the dates for several temperatures and odds. A 30% spring date means a 3-in-10 chance of a later frost (the convention almanacs use); 50% is the median; 10% the cautious date.
| Threshold | Spring, 10% | Spring, 30% | Spring, 50% | Spring, 90% | Autumn, 50% | Autumn, 10% |
|---|---|---|---|---|---|---|
| 36°F (light frost) | April 2 | March 20 | March 10 | February 20 | November 16 | November 1 |
| 32°F | March 17 | March 6 | February 26 | January 29 | November 28 | November 7 |
| 28°F (hard freeze) | March 7 | February 21 | February 9 | January 2 | December 13 | November 21 |
| 24°F | February 26 | February 7 | January 22 | December 17 | January 1 | December 2 |
Source: NOAA NCEI 1991-2020 annual normals; ZIP centers: Census Bureau 2024 Gazetteer; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026. Autumn 10%: one year in ten has its first frost before this date.