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 58505
The USDA's 2023 Plant Hardiness Zone Map puts ZIP 58505 in zone 4a (the coldest night of a typical year: -30 to -25°F).
The nearest station, Bismarck (2.4 mi NNW), ND, is 1 miles from the ZIP's center: its last spring frost comes after May 10 in half of years and after May 23 in one year in ten.
| Station | Distance | Elevation | Last frost (median) | 1 in 10 after | First frost (median) | Hardiness zone |
|---|---|---|---|---|---|---|
| Bismarck (2.4 mi NNW), ND | 1 mi | 1,831 ft | May 10 | May 23 | September 30 | – |
| Bismarck Weather Office, ND | 4 mi | 1,651 ft | May 14 | May 27 | September 30 | – |
| Bismarck, NDBismarck Municipal Airport | 4 mi | 1,658 ft | May 14 | May 27 | September 27 | 4a |
| Mandan, NDMandan Experiment Station | 6 mi | 1,750 ft | May 13 | May 26 | September 27 | 4b |
| Wilton, ND | 23 mi | 2,188 ft | May 11 | May 25 | September 30 | – |
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 Bismarck (2.4 mi NNW)
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 2 | May 25 | May 20 | May 8 | September 21 | September 8 |
| 32°F | May 23 | May 14 | May 10 | April 30 | September 30 | September 16 |
| 28°F (hard freeze) | May 13 | May 6 | May 1 | April 18 | October 9 | September 25 |
| 24°F | May 4 | April 28 | April 21 | April 8 | October 18 | October 2 |
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.