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 53186
The USDA's 2023 Plant Hardiness Zone Map puts ZIP 53186 in zone 5b (the coldest night of a typical year: -15 to -10°F).
The nearest station, Brookfield, WI, is 2 miles from the ZIP's center: its last spring frost comes after April 30 in half of years and after May 15 in one year in ten.
| Station | Distance | Elevation | Last frost (median) | 1 in 10 after | First frost (median) | Hardiness zone |
|---|---|---|---|---|---|---|
| Brookfield, WIBrookfield Wastewater Treatment Plant | 2 mi | 830 ft | April 30 | May 15 | October 14 | – |
| Waukesha, WIWaukesha Wastewater Treatment Plant | 2 mi | 789 ft | May 1 | May 18 | October 13 | 5b |
| Wauwatosa, WIMount Mary College | 10 mi | 715 ft | April 26 | May 12 | October 18 | 6a |
| West Allis, WI | 10 mi | 723 ft | April 26 | May 12 | October 22 | – |
| Hales Corners, WIHales Corners/Whitnall Park/Bo | 11 mi | 774 ft | May 3 | May 19 | October 14 | 5b |
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 Brookfield
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 19 | May 10 | April 28 | October 3 | September 21 |
| 32°F | May 15 | May 5 | April 30 | April 16 | October 14 | September 28 |
| 28°F (hard freeze) | May 3 | April 26 | April 19 | April 5 | October 25 | October 10 |
| 24°F | April 23 | April 14 | April 8 | March 24 | November 5 | October 25 |
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.