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 92121
The USDA's 2023 Plant Hardiness Zone Map puts ZIP 92121 in zone 10b (the coldest night of a typical year: 35 to 40°F).
The nearest station, Rancho Bernardo, CA, is 11 miles from the ZIP's center: a night at 32°F or colder comes there in only 21% of years, and NOAA's median date of the last spring frost is January 5. 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 |
|---|---|---|---|---|---|---|
| Rancho Bernardo, CA | 11 mi | 690 ft | January 5 | February 1 | January 2 | 10a |
| Escondido, CAEscondido #2 | 17 mi | 600 ft | January 2 | February 4 | December 30 | – |
| El Cajon, CA | 17 mi | 495 ft | January 6 | February 7 | December 21 | 10a |
| San Pasqual Animal Park, CA | 18 mi | 420 ft | February 2 | March 4 | December 7 | 9b |
| Ramona Fire Dept, CA | 19 mi | 1,470 ft | March 4 | April 10 | December 4 | – |
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 Rancho Bernardo
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 28 | February 8 | January 23 | December 17 | December 23 | December 1 |
| 32°F | February 1 | January 15 | January 5 | December 13 | January 2 | December 13 |
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.