Frost dates for Hillsboro, WI
At Hillsboro, the median last spring frost (32°F) is May 5 and the median first fall frost is Oct 4, for a typical growing season of 153 days. For a 90% chance that the last frost has passed, wait until May 18. Nearby ZIP codes are in USDA hardiness zones 4b to 5a.
- May 5Last spring frost (median)50% chance of 32°F after this date
- May 18Safer planting date10% chance of 32°F after this date
- Oct 4First fall frost (median)50% chance of 32°F by this date
- 153 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 3 | May 16 | May 30 |
| 32°F | Apr 22 | May 5 | May 18 |
| 28°F | Apr 9 | Apr 23 | May 7 |
| 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 14 | Sep 27 | Oct 8 |
| 32°F | Sep 23 | Oct 4 | Oct 18 |
| 28°F | Oct 2 | Oct 17 | Nov 1 |
| 24°F | Oct 15 | Oct 28 | Nov 12 |
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 | 114 days | 133 days | 151 days |
| 32°F | 135 days | 153 days | 173 days |
| 28°F | 157 days | 176 days | 196 days |
| 24°F | 180 days | 201 days | 220 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 |
|---|---|---|---|
| 53962 | 4b | -25 to -20°F | 6 km |
| 53968 | 5a | -20 to -15°F | 8 km |
| 53929 | 5a | -20 to -15°F | 12 km |
| 54638 | 5a | -20 to -15°F | 16 km |
| 54670 | 5a | -20 to -15°F | 24 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 USC00473654, at 43.6542, -90.3339, elevation 286 m (940 ft).
- Data quality: Representative (10+ years), 17 years of freeze data.
- Average days per year at or below 32°F: 162.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Hillsboro 2sw (4 km)
- Mauston 1 SE (27 km)
- Reedsburg (31 km)
- Richland Center (36 km)
- Cashton (37 km)
- Rock Springs 3 SW (37 km)
- Cashton 3nnw (40 km)
- Viroqua (45 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.