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 78109
The USDA's 2023 Plant Hardiness Zone Map puts ZIP 78109 in zone 9a (the coldest night of a typical year: 20 to 25°F).
The nearest station, Randolph AFB, TX, is 5 miles from the ZIP's center: its last spring frost comes after February 21 in half of years and after March 14 in one year in ten.
| Station | Distance | Elevation | Last frost (median) | 1 in 10 after | First frost (median) | Hardiness zone |
|---|---|---|---|---|---|---|
| Randolph AFB, TXRandolph Air Force Base | 5 mi | 760 ft | February 21 | March 14 | December 5 | – |
| San Antonio Incarnate Word, TX | 11 mi | 700 ft | February 25 | March 19 | November 28 | 9a |
| San Antonio, TXSan Antonio International Airport | 12 mi | 789 ft | February 26 | March 17 | November 28 | 9a |
| San Antonio Stinson Airport, TX | 14 mi | 571 ft | February 20 | March 13 | December 3 | 9a |
| New Braunfels, TX | 15 mi | 720 ft | March 8 | April 1 | November 18 | – |
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 Randolph AFB
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 26 | March 14 | March 6 | February 13 | November 24 | November 4 |
| 32°F | March 14 | March 2 | February 21 | January 10 | December 5 | November 16 |
| 28°F (hard freeze) | March 5 | February 15 | January 26 | December 18 | December 19 | November 28 |
| 24°F | February 24 | January 26 | January 4 | December 11 | December 28 | December 6 |
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.