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 78521
The USDA's 2023 Plant Hardiness Zone Map puts ZIP 78521 in zone 10a (the coldest night of a typical year: 30 to 35°F).
The nearest station, Brownsville, TX, is 7 miles from the ZIP's center: a night at 32°F or colder comes there in only 26% of years, and NOAA's median date of the last spring frost is January 6. By the USDA's method its plant hardiness zone is 10a.
| Station | Distance | Elevation | Last frost (median) | 1 in 10 after | First frost (median) | Hardiness zone |
|---|---|---|---|---|---|---|
| Brownsville, TXBrownsville S Padre Island International Airport | 7 mi | 23 ft | January 6 | February 1 | January 2 | 10a |
| Weather Office Brownsville, TX | 7 mi | 15 ft | January 9 | March 1 | January 4 | – |
| Port Isabel station, TX | 10 mi | 17 ft | January 3 | February 2 | January 1 | – |
| Port Isabel, TXPort Isabel Cameron Airport | 15 mi | 19 ft | January 8 | February 7 | January 4 | 10a |
| Harlingen station, TX | 28 mi | 38 ft | January 9 | February 4 | January 3 | 10a |
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 Brownsville
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) | February 18 | January 30 | January 16 | December 19 | December 30 | November 30 |
| 32°F | February 1 | January 13 | January 6 | December 11 | January 2 | December 8 |
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.