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 50702
The USDA's 2023 Plant Hardiness Zone Map puts ZIP 50702 in zone 5a (the coldest night of a typical year: -20 to -15°F).
The nearest station, Waterloo, IA, is 8 miles from the ZIP's center: its last spring frost comes after April 27 in half of years and after May 10 in one year in ten. By the USDA's method its plant hardiness zone is 5a.
| Station | Distance | Elevation | Last frost (median) | 1 in 10 after | First frost (median) | Hardiness zone |
|---|---|---|---|---|---|---|
| Waterloo, IAWaterloo Municipal Airport | 8 mi | 868 ft | April 27 | May 10 | October 10 | 5a |
| Independence, IAIndependence #1 | 23 mi | 1,010 ft | April 30 | May 12 | October 7 | – |
| Grundy Center, IA | 24 mi | 985 ft | April 29 | May 12 | October 9 | 5a |
| Oelwein, IA2 mi S | 24 mi | 1,010 ft | April 30 | May 13 | October 9 | – |
| Tripoli, IA | 24 mi | 1,055 ft | April 29 | May 9 | October 9 | 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 Waterloo
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 17 | May 10 | May 6 | April 23 | September 30 | September 16 |
| 32°F | May 10 | May 2 | April 27 | April 11 | October 10 | September 26 |
| 28°F (hard freeze) | May 2 | April 22 | April 16 | April 3 | October 20 | October 6 |
| 24°F | April 22 | April 13 | April 7 | March 22 | October 29 | October 17 |
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.