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 78251
The USDA's 2023 Plant Hardiness Zone Map puts ZIP 78251 in zone 9a (the coldest night of a typical year: 20 to 25°F).
The nearest station, San Antonio/Seaworld, TX, is 2 miles from the ZIP's center: its last spring frost comes after February 18 in half of years and after March 16 in one year in ten.
| Station | Distance | Elevation | Last frost (median) | 1 in 10 after | First frost (median) | Hardiness zone |
|---|---|---|---|---|---|---|
| San Antonio/Seaworld, TX | 2 mi | 940 ft | February 18 | March 16 | December 9 | – |
| San Antonio Kelly Air Force Base, TX | 8 mi | 682 ft | February 22 | March 12 | December 2 | – |
| San Antonio Incarnate Word, TX | 12 mi | 700 ft | February 25 | March 19 | November 28 | 9a |
| San Antonio, TXSan Antonio International Airport | 13 mi | 789 ft | February 26 | March 17 | November 28 | 9a |
| 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/Seaworld
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) | March 31 | March 14 | March 4 | February 11 | November 25 | November 5 |
| 32°F | March 16 | February 28 | February 18 | January 18 | December 9 | November 17 |
| 28°F (hard freeze) | March 3 | February 14 | January 31 | December 17 | December 29 | November 28 |
| 24°F | February 22 | February 5 | January 19 | December 8 | January 3 | December 4 |
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.