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 92139
The USDA's 2023 Plant Hardiness Zone Map puts ZIP 92139 in zone 10b (the coldest night of a typical year: 35 to 40°F).
The nearest station, San Diego Brown Field, CA, is 8 miles from the ZIP's center: a night at 32°F or colder comes there in only 25% 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 |
|---|---|---|---|---|---|---|
| San Diego Brown Field, CA | 8 mi | 515 ft | January 6 | February 5 | December 31 | 10a |
| El Cajon, CA | 11 mi | 495 ft | January 6 | February 7 | December 21 | 10a |
| Alpine, CA | 19 mi | 1,695 ft | February 12 | March 20 | December 24 | 10a |
| El Capitan Dam, CA | 20 mi | 600 ft | March 19 | June 1 | December 8 | – |
| Rancho Bernardo, CA | 24 mi | 690 ft | January 5 | February 1 | January 2 | 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 San Diego Brown Field
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 7 | February 17 | February 2 | December 29 | December 20 | December 1 |
| 32°F | February 5 | January 17 | January 6 | December 13 | December 31 | December 11 |
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.