Frost dates for Waukesha Wastewater Plant, WI
At Waukesha Wastewater Plant, the median last spring frost (32°F) is May 1 and the median first fall frost is Oct 13, for a typical growing season of 162 days. For a 90% chance that the last frost has passed, wait until May 18. Nearby ZIP codes are in USDA hardiness zone 5b.
- May 1Last spring frost (median)50% chance of 32°F after this date
- May 18Safer planting date10% chance of 32°F after this date
- Oct 13First fall frost (median)50% chance of 32°F by this date
- 162 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 29 | May 13 | May 29 |
| 32°F | Apr 18 | May 1 | May 18 |
| 28°F | Apr 6 | Apr 19 | May 5 |
| 24°F | Mar 27 | Apr 7 | Apr 21 |
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 | Sep 20 | Oct 2 | Oct 15 |
| 32°F | Sep 29 | Oct 13 | Oct 25 |
| 28°F | Oct 8 | Oct 23 | Nov 6 |
| 24°F | Oct 22 | Nov 4 | Nov 18 |
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 | 123 days | 141 days | 159 days |
| 32°F | 144 days | 162 days | 183 days |
| 28°F | 164 days | 185 days | 205 days |
| 24°F | 188 days | 210 days | 229 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 |
|---|---|---|---|
| 53188 | 5b | -15 to -10°F | 4 km |
| 53189 | 5b | -15 to -10°F | 8 km |
| 53146 | 5b | -15 to -10°F | 8 km |
| 53183 | 5b | -15 to -10°F | 10 km |
| 53127 | 5b | -15 to -10°F | 12 km |
| 53103 | 5b | -15 to -10°F | 14 km |
| 53149 | 5b | -15 to -10°F | 16 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 USC00478937, at 43.0064, -88.2492, elevation 240 m (789 ft).
- Data quality: Representative (10+ years), 21 years of freeze data.
- Average days per year at or below 32°F: 143.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Brookfield Wastewater Plant (8 km)
- Mount Mary College (19 km)
- Hales Corners/whitnall Park/bo (19 km)
- West Allis (20 km)
- Richfield 3 SSW (23 km)
- Oconomowoc Wastewater Plant (23 km)
- Sullivan 3se (25 km)
- Germantown (28 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.