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 52246
The USDA's 2023 Plant Hardiness Zone Map puts ZIP 52246 in zone 5b (the coldest night of a typical year: -15 to -10°F).
The nearest station, Iowa City, IA, is 3 miles from the ZIP's center: its last spring frost comes after April 21 in half of years and after May 6 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 |
|---|---|---|---|---|---|---|
| Iowa City, IAIowa City Municipal Airport | 3 mi | 650 ft | April 21 | May 6 | October 18 | 5b |
| Iowa City station, IA | 5 mi | 640 ft | April 29 | May 14 | October 9 | 5b |
| Cedar Rapids, IACedar Rapids Municipal Airport | 17 mi | 868 ft | April 27 | May 11 | October 11 | 5a |
| Williamsburg, IA1 mi E | 21 mi | 780 ft | April 28 | May 12 | October 9 | 5a |
| Tipton, IA | 26 mi | 820 ft | April 21 | May 4 | October 15 | 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 Iowa City
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 15 | May 6 | May 1 | April 17 | October 9 | September 26 |
| 32°F | May 6 | April 28 | April 21 | April 5 | October 18 | October 4 |
| 28°F (hard freeze) | April 27 | April 16 | April 9 | March 25 | October 28 | October 15 |
| 24°F | April 15 | April 5 | March 31 | March 11 | November 6 | October 26 |
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.