Frost dates for Mount Mary College, WI
At Mount Mary College, the median last spring frost (32°F) is Apr 26 and the median first fall frost is Oct 18, for a typical growing season of 173 days. For a 90% chance that the last frost has passed, wait until May 12. Nearby ZIP codes are in USDA hardiness zones 5b to 6a.
- Apr 26Last spring frost (median)50% chance of 32°F after this date
- May 12Safer planting date10% chance of 32°F after this date
- Oct 18First fall frost (median)50% chance of 32°F by this date
- 173 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 24 | May 8 | May 24 |
| 32°F | Apr 12 | Apr 26 | May 12 |
| 28°F | Apr 1 | Apr 14 | Apr 30 |
| 24°F | Mar 20 | Apr 4 | Apr 17 |
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 25 | Oct 6 | Oct 22 |
| 32°F | Oct 2 | Oct 18 | Nov 1 |
| 28°F | Oct 13 | Oct 30 | Nov 11 |
| 24°F | Oct 27 | Nov 9 | Nov 23 |
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 | 130 days | 150 days | 168 days |
| 32°F | 153 days | 173 days | 192 days |
| 28°F | 178 days | 196 days | 217 days |
| 24°F | 202 days | 220 days | 237 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 |
|---|---|---|---|
| 53222 | 5b | -15 to -10°F | 1 km |
| 53226 | 5b | -15 to -10°F | 3 km |
| 53213 | 5b | -15 to -10°F | 3 km |
| 53210 | 6a | -10 to -5°F | 5 km |
| 53216 | 6a | -10 to -5°F | 5 km |
| 53225 | 5b | -15 to -10°F | 5 km |
| 53007 | 5b | -15 to -10°F | 5 km |
| 53122 | 5b | -15 to -10°F | 5 km |
| 53218 | 6a | -10 to -5°F | 5 km |
| 53005 | 5b | -15 to -10°F | 6 km |
| 53206 | 6a | -10 to -5°F | 8 km |
| 53209 | 6a | -10 to -5°F | 9 km |
| 53212 | 6a | -10 to -5°F | 10 km |
| 53224 | 5b | -15 to -10°F | 10 km |
| 53223 | 6a | -10 to -5°F | 10 km |
| 53211 | 6a | -10 to -5°F | 12 km |
| 53217 | 6a | -10 to -5°F | 13 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 USC00475474, at 43.0722, -88.0294, elevation 218 m (715 ft).
- Data quality: Standard (24+ years of data), 28 years of freeze data.
- Average days per year at or below 32°F: 134.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- West Allis (6 km)
- Brookfield Wastewater Plant (12 km)
- Hales Corners/whitnall Park/bo (15 km)
- Milwaukee Mitchell Airport (17 km)
- Waukesha Wastewater Plant (19 km)
- Germantown (20 km)
- Richfield 3 SSW (21 km)
- South Milwaukee Wastewater Plant (24 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.