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 99929
The USDA's 2023 Plant Hardiness Zone Map puts ZIP 99929 in zone 7b (the coldest night of a typical year: 5 to 10°F).
The nearest station, Wrangell, AK, is 25 miles from the ZIP's center: its last spring frost comes after April 11 in half of years and after April 29 in one year in ten. By the USDA's method its plant hardiness zone is 7b.
| Station | Distance | Elevation | Last frost (median) | 1 in 10 after | First frost (median) | Hardiness zone |
|---|---|---|---|---|---|---|
| Wrangell, AKWrangell Airport | 25 mi | 56 ft | April 11 | April 29 | November 1 | 7b |
| Thorne Bay, AK | 43 mi | 286 ft | May 1 | May 16 | October 13 | – |
| Ketchikan (10 mi N), AK | 53 mi | 295 ft | April 20 | May 4 | October 26 | – |
| Petersburg, AKPetersburg 1 | 56 mi | 107 ft | April 29 | May 14 | October 17 | 7a |
| Ketchikan, AKKetchikan International Airport | 60 mi | 76 ft | April 22 | May 9 | October 23 | 7b |
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 Wrangell
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) | May 14 | May 5 | April 30 | April 16 | October 16 | September 30 |
| 32°F | April 29 | April 19 | April 11 | March 26 | November 1 | October 13 |
| 28°F (hard freeze) | April 9 | March 31 | March 24 | March 4 | November 18 | October 31 |
| 24°F | March 25 | March 14 | March 6 | February 5 | December 1 | November 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.