Frost dates for Delavan Wastewater Plant, WI
At Delavan Wastewater Plant, the median last spring frost (32°F) is Apr 28 and the median first fall frost is Oct 14, for a typical growing season of 168 days. For a 90% chance that the last frost has passed, wait until May 14. Nearby ZIP codes are in USDA hardiness zone 5b.
- Apr 28Last spring frost (median)50% chance of 32°F after this date
- May 14Safer planting date10% chance of 32°F after this date
- Oct 14First fall frost (median)50% chance of 32°F by this date
- 168 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 10 | May 26 |
| 32°F | Apr 12 | Apr 28 | May 14 |
| 28°F | Apr 2 | Apr 15 | May 1 |
| 24°F | Mar 17 | Apr 3 | Apr 18 |
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 3 | Oct 15 |
| 32°F | Sep 28 | Oct 14 | Oct 26 |
| 28°F | Oct 8 | Oct 25 | Nov 8 |
| 24°F | Oct 25 | Nov 7 | Nov 22 |
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 | 124 days | 145 days | 165 days |
| 32°F | 146 days | 168 days | 188 days |
| 28°F | 170 days | 192 days | 213 days |
| 24°F | 197 days | 218 days | 240 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 |
|---|---|---|---|
| 53115 | 5b | -15 to -10°F | 2 km |
| 53114 | 5b | -15 to -10°F | 8 km |
| 53585 | 5b | -15 to -10°F | 13 km |
| 53184 | 5b | -15 to -10°F | 13 km |
| 53121 | 5b | -15 to -10°F | 14 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 USC00472051, at 42.6364, -88.6608, elevation 269 m (882 ft).
- Data quality: Estimated from nearby stations (2+ years), 8 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
- Lake Geneva Wastewater Plant (20 km)
- Clinton Wastewater Plant (20 km)
- Whitewater (24 km)
- Pell Lake (29 km)
- Afton - Janesville Wastewater Plant (33 km)
- Burlington (33 km)
- Beloit (34 km)
- Fort Atkinson (34 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.