Frost dates for Willmar Wastewater Plant, MN
At Willmar Wastewater Plant, the median last spring frost (32°F) is Apr 30 and the median first fall frost is Oct 7, for a typical growing season of 159 days. For a 90% chance that the last frost has passed, wait until May 13. Nearby ZIP codes are in USDA hardiness zone 4b.
- Apr 30Last spring frost (median)50% chance of 32°F after this date
- May 13Safer planting date10% chance of 32°F after this date
- Oct 7First fall frost (median)50% chance of 32°F by this date
- 159 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 27 | May 9 | May 23 |
| 32°F | Apr 16 | Apr 30 | May 13 |
| 28°F | Apr 5 | Apr 19 | May 2 |
| 24°F | Mar 27 | Apr 10 | Apr 24 |
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 16 | Sep 29 | Oct 11 |
| 32°F | Sep 23 | Oct 7 | Oct 21 |
| 28°F | Oct 2 | Oct 19 | Oct 31 |
| 24°F | Oct 15 | Oct 29 | Nov 10 |
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 | 122 days | 142 days | 160 days |
| 32°F | 142 days | 159 days | 178 days |
| 28°F | 160 days | 179 days | 200 days |
| 24°F | 181 days | 200 days | 219 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 |
|---|---|---|---|
| 56201 | 4b | -25 to -20°F | 1 km |
| 56251 | 4b | -25 to -20°F | 10 km |
| 56282 | 4b | -25 to -20°F | 17 km |
| 56209 | 4b | -25 to -20°F | 18 km |
| 56216 | 4b | -25 to -20°F | 18 km |
| 56281 | 4b | -25 to -20°F | 20 km |
| 56253 | 4b | -25 to -20°F | 21 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 USC00219004, at 45.1078, -95.0358, elevation 335 m (1,100 ft).
- Data quality: Representative (10+ years), 19 years of freeze data.
- Average days per year at or below 32°F: 166.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Willmar 5n (9 km)
- New London (23 km)
- Olivia 3e (39 km)
- Litchfield (39 km)
- Benson (51 km)
- Granite Falls (52 km)
- Hutchinson 1 N (57 km)
- Montevideo 1sw (59 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.