Frost dates for Union Grove, WI
At Union Grove, the median last spring frost (32°F) is May 5 and the median first fall frost is Oct 8, for a typical growing season of 156 days. For a 90% chance that the last frost has passed, wait until May 20. Nearby ZIP codes are in USDA hardiness zone 5b.
- May 5Last spring frost (median)50% chance of 32°F after this date
- May 20Safer planting date10% chance of 32°F after this date
- Oct 8First fall frost (median)50% chance of 32°F by this date
- 156 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 | May 1 | May 17 | May 31 |
| 32°F | Apr 21 | May 5 | May 20 |
| 28°F | Apr 9 | Apr 23 | May 10 |
| 24°F | Mar 29 | Apr 11 | Apr 27 |
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 18 | Sep 30 | Oct 12 |
| 32°F | Sep 27 | Oct 8 | Oct 23 |
| 28°F | Oct 4 | Oct 20 | Nov 3 |
| 24°F | Oct 15 | Nov 1 | Nov 16 |
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 | 118 days | 136 days | 155 days |
| 32°F | 138 days | 156 days | 175 days |
| 28°F | 159 days | 178 days | 199 days |
| 24°F | 181 days | 202 days | 224 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 |
|---|---|---|---|
| 53182 | 5b | -15 to -10°F | 1 km |
| 53139 | 5b | -15 to -10°F | 7 km |
| 53177 | 5b | -15 to -10°F | 8 km |
| 53126 | 5b | -15 to -10°F | 12 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 USC00478723, at 42.6903, -88.0336, elevation 222 m (730 ft).
- Data quality: Representative (10+ years), 22 years of freeze data.
- Average days per year at or below 32°F: 145.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Paddock Lake (13 km)
- Kenosha Regional Airport (13 km)
- Rochester Wastewater Plant (16 km)
- Burlington (19 km)
- Racine Batten Airport (20 km)
- Racine (20 km)
- Kenosha (23 km)
- Hales Corners/whitnall Park/bo (27 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.