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 53220
The USDA's 2023 Plant Hardiness Zone Map puts ZIP 53220 in zone 5b (the coldest night of a typical year: -15 to -10°F).
The nearest station, Hales Corners, WI, is 3 miles from the ZIP's center: its last spring frost comes after May 3 in half of years and after May 19 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 |
|---|---|---|---|---|---|---|
| Hales Corners, WIHales Corners/Whitnall Park/Bo | 3 mi | 774 ft | May 3 | May 19 | October 14 | 5b |
| West Allis, WI | 4 mi | 723 ft | April 26 | May 12 | October 22 | – |
| Milwaukee, WIMilwaukee Mitchell Airport | 4 mi | 670 ft | April 19 | May 2 | October 29 | 6a |
| Wauwatosa, WIMount Mary College | 8 mi | 715 ft | April 26 | May 12 | October 18 | 6a |
| South Milwaukee, WISouth Milwaukee Wastewater Treatment Plant | 8 mi | 650 ft | April 22 | May 8 | October 26 | – |
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 Hales Corners
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 29 | May 20 | May 14 | April 30 | October 3 | September 22 |
| 32°F | May 19 | May 9 | May 3 | April 18 | October 14 | September 30 |
| 28°F (hard freeze) | May 9 | April 29 | April 21 | April 8 | October 24 | October 8 |
| 24°F | April 25 | April 15 | April 9 | March 27 | November 4 | October 23 |
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.