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 99507
The USDA's 2023 Plant Hardiness Zone Map puts ZIP 99507 in zone 5a (the coldest night of a typical year: -20 to -15°F).
The nearest station, Glen Alps, AK, is 3 miles from the ZIP's center: its last spring frost comes after May 18 in half of years and after May 31 in one year in ten. By the USDA's method its plant hardiness zone is 5b.
| Station | Distance | Elevation | Last frost (median) | 1 in 10 after | First frost (median) | Hardiness zone |
|---|---|---|---|---|---|---|
| Glen Alps, AK | 3 mi | 2,202 ft | May 18 | May 31 | September 23 | 5b |
| Anchorage Upper De Armoun, AK | 3 mi | 1,335 ft | May 7 | May 23 | September 28 | – |
| Anchorage Rabbit Creek #2, AK | 5 mi | 913 ft | May 12 | May 24 | September 26 | – |
| Campbell Creek Science Center, AK | 6 mi | 258 ft | May 28 | June 6 | September 12 | – |
| Fort Richardson Water Treatment Plant, AK | 8 mi | 470 ft | May 9 | May 22 | September 26 | 5a |
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 Glen Alps
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) | June 20 | June 11 | June 5 | May 21 | September 11 | August 25 |
| 32°F | May 31 | May 24 | May 18 | May 4 | September 23 | September 8 |
| 28°F (hard freeze) | May 17 | May 9 | May 4 | April 17 | October 2 | September 20 |
| 24°F | May 6 | April 30 | April 21 | April 8 | October 12 | September 29 |
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.