Frost dates for South Milwaukee Wastewater Plant, WI
At South Milwaukee Wastewater Plant, the median last spring frost (32°F) is Apr 22 and the median first fall frost is Oct 26, for a typical growing season of 184 days. For a 90% chance that the last frost has passed, wait until May 8. Nearby ZIP codes are in USDA hardiness zone 6a.
- Apr 22Last spring frost (median)50% chance of 32°F after this date
- May 8Safer planting date10% chance of 32°F after this date
- Oct 26First fall frost (median)50% chance of 32°F by this date
- 184 daysGrowing season (median)between 32°F freezes
Last spring frost dates
The chance that the temperature drops to the threshold after each date.
| Temperature | 90% chance later | 50% chance later | 10% chance later |
|---|---|---|---|
| 36°F | Apr 21 | May 5 | May 24 |
| 32°F | Apr 9 | Apr 22 | May 8 |
| 28°F | Mar 28 | Apr 9 | Apr 24 |
| 24°F | Mar 15 | Mar 31 | Apr 13 |
First fall frost dates
The chance that the temperature has dropped to the threshold by each date.
| Temperature | 10% chance by | 50% chance by | 90% chance by |
|---|---|---|---|
| 36°F | Oct 1 | Oct 16 | Oct 28 |
| 32°F | Oct 10 | Oct 26 | Nov 8 |
| 28°F | Oct 24 | Nov 5 | Nov 20 |
| 24°F | Nov 3 | Nov 15 | Dec 1 |
Growing season length
Days between the last spring and first fall freeze, as the length reached in 9, 5 and 1 out of 10 years.
| Temperature | 9 in 10 years at least | 5 in 10 years at least | 1 in 10 years at least |
|---|---|---|---|
| 36°F | 140 days | 162 days | 179 days |
| 32°F | 163 days | 184 days | 203 days |
| 28°F | 188 days | 208 days | 226 days |
| 24°F | 210 days | 229 days | 249 days |
Chance of a freeze in any year
| Temperature | Chance per year |
|---|---|
| 36°F | 100% |
| 32°F | 100% |
| 28°F | 100% |
| 24°F | 100% |
ZIP codes whose closest station is this one
| ZIP | Hardiness zone | Avg. extreme low | Distance |
|---|---|---|---|
| 53172 | 6a | -10 to -5°F | 1 km |
| 53154 | 6a | -10 to -5°F | 5 km |
Not the official USDA Plant Hardiness Zone Map. Zones shown here are the values published in the USDA-ARS / Oregon State University PRISM Group 2023 ZIP code tables, shown unaltered. For the official interactive map, visit planthardiness.ars.usda.gov.
About this station
- NOAA station ID USC00477964, at 42.9011, -87.8494, elevation 198 m (650 ft).
- Data quality: Representative (10+ years), 14 years of freeze data.
- Average days per year at or below 32°F: 124.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Milwaukee Mitchell Airport (7 km)
- Hales Corners/whitnall Park/bo (15 km)
- Racine Batten Airport (16 km)
- West Allis (18 km)
- Racine (23 km)
- Mount Mary College (24 km)
- Union Grove (28 km)
- Brookfield Wastewater Plant (32 km)
Sources
- NOAA National Centers for Environmental Information, U.S. Climate Normals 1991–2020, annual/seasonal normals by station (version 1.0.1), file dated June 27, 2023; documentation.
- USDA Agricultural Research Service and PRISM Group, Oregon State University, 2023 Plant Hardiness Zone Map ZIP code tables (CONUS, Alaska, Hawaii, Puerto Rico), files dated November 17, 2023. Data © PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed November 1, 2026. Official map: planthardiness.ars.usda.gov.
- U.S. Census Bureau, 2024 Gazetteer ZIP Code Tabulation Areas file, dated August 30, 2024 (ZIP centroids used to find the nearest station).
Freeze dates are 30-year probabilities, not forecasts. Check your local forecast before planting tender plants.