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 78666
The USDA's 2023 Plant Hardiness Zone Map puts ZIP 78666 in zone 9a (the coldest night of a typical year: 20 to 25°F).
The nearest station, San Marcos, TX, is 2 miles from the ZIP's center: its last spring frost comes after February 28 in half of years and after March 21 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 Marcos, TX | 2 mi | 665 ft | February 28 | March 21 | November 29 | 9a |
| New Braunfels Weather Office, TX | 13 mi | 628 ft | February 25 | March 20 | November 25 | – |
| Austin San Antonio, TX | 13 mi | 633 ft | March 1 | March 20 | November 26 | 9a |
| Canyon Lake, TXCanyon Dam | 13 mi | 1,000 ft | March 1 | March 22 | December 1 | 9a |
| New Braunfels, TX | 19 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 San Marcos
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 5 | March 24 | March 14 | February 23 | November 16 | November 1 |
| 32°F | March 21 | March 8 | February 28 | February 1 | November 29 | November 8 |
| 28°F (hard freeze) | March 8 | February 25 | February 13 | January 9 | December 15 | November 19 |
| 24°F | February 28 | February 8 | January 29 | December 26 | January 2 | December 5 |
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.