Frost dates for Portage Wastewater Plant, WI
At Portage Wastewater Plant, the median last spring frost (32°F) is Apr 28 and the median first fall frost is Oct 10, for a typical growing season of 164 days. For a 90% chance that the last frost has passed, wait until May 12. Nearby ZIP codes are in USDA hardiness zone 5a.
- Apr 28Last spring frost (median)50% chance of 32°F after this date
- May 12Safer planting date10% chance of 32°F after this date
- Oct 10First fall frost (median)50% chance of 32°F by this date
- 164 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 26 | May 8 | May 24 |
| 32°F | Apr 14 | Apr 28 | May 12 |
| 28°F | Apr 4 | Apr 16 | Apr 30 |
| 24°F | Mar 23 | Apr 6 | Apr 20 |
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 17 | Sep 30 | Oct 11 |
| 32°F | Sep 26 | Oct 10 | Oct 23 |
| 28°F | Oct 6 | Oct 22 | Nov 4 |
| 24°F | Oct 21 | Nov 2 | Nov 17 |
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 | 126 days | 145 days | 162 days |
| 32°F | 145 days | 164 days | 184 days |
| 28°F | 167 days | 188 days | 207 days |
| 24°F | 191 days | 210 days | 230 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 |
|---|---|---|---|
| 53901 | 5a | -20 to -15°F | 5 km |
| 53954 | 5a | -20 to -15°F | 10 km |
| 53969 | 5a | -20 to -15°F | 12 km |
| 53930 | 5a | -20 to -15°F | 18 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 USC00476718, at 43.5306, -89.4369, elevation 239 m (785 ft).
- Data quality: Standard (24+ years of data), 30 years of freeze data.
- Average days per year at or below 32°F: 148.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Dalton (23 km)
- Lodi (24 km)
- Baraboo (25 km)
- Arlington (26 km)
- Wisconsin Dells (28 km)
- Montello (29 km)
- Sauk City Wastewater Plant (38 km)
- Markesan (40 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.