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 52401
The USDA's 2023 Plant Hardiness Zone Map puts ZIP 52401 in zone 5b (the coldest night of a typical year: -15 to -10°F).
The nearest station, Marion, IA, is 6 miles from the ZIP's center: its last spring frost comes after April 28 in half of years and after May 13 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 |
|---|---|---|---|---|---|---|
| Marion, IACedar Rapids #1 | 6 mi | 813 ft | April 28 | May 13 | October 12 | 5b |
| Cedar Rapids, IACedar Rapids Municipal Airport | 7 mi | 868 ft | April 27 | May 11 | October 11 | 5a |
| Anamosa (3 mi SSW), IA | 20 mi | 906 ft | April 27 | May 10 | October 13 | – |
| Anamosa, IA1 mi WNW | 21 mi | 805 ft | May 1 | May 18 | October 4 | 5a |
| Coggon, IA | 22 mi | 903 ft | May 3 | May 17 | October 7 | – |
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 Marion
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 22 | May 13 | May 7 | April 23 | October 2 | September 19 |
| 32°F | May 13 | May 4 | April 28 | April 14 | October 12 | September 29 |
| 28°F (hard freeze) | May 2 | April 24 | April 17 | April 4 | October 22 | October 8 |
| 24°F | April 22 | April 12 | April 6 | March 23 | October 31 | October 19 |
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.