Frost dates for Mahnomen, MN
At Mahnomen, the median last spring frost (32°F) is May 7 and the median first fall frost is Sep 28, for a typical growing season of 143 days. For a 90% chance that the last frost has passed, wait until May 24. Nearby ZIP codes are in USDA hardiness zones 3b to 4a.
- May 7Last spring frost (median)50% chance of 32°F after this date
- May 24Safer planting date10% chance of 32°F after this date
- Sep 28First fall frost (median)50% chance of 32°F by this date
- 143 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 5 | May 19 | Jun 5 |
| 32°F | Apr 27 | May 7 | May 24 |
| 28°F | Apr 15 | Apr 29 | May 12 |
| 24°F | Apr 6 | Apr 19 | May 2 |
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 3 | Sep 19 | Oct 1 |
| 32°F | Sep 15 | Sep 28 | Oct 13 |
| 28°F | Sep 23 | Oct 8 | Oct 25 |
| 24°F | Oct 3 | Oct 21 | Nov 4 |
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 | 98 days | 121 days | 140 days |
| 32°F | 122 days | 143 days | 161 days |
| 28°F | 142 days | 162 days | 182 days |
| 24°F | 162 days | 184 days | 204 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 |
|---|---|---|---|
| 56557 | 4a | -30 to -25°F | 10 km |
| 56516 | 4a | -30 to -25°F | 14 km |
| 56541 | 4a | -30 to -25°F | 21 km |
| 56589 | 4a | -30 to -25°F | 22 km |
| 56545 | 4a | -30 to -25°F | 22 km |
| 56566 | 3b | -35 to -30°F | 29 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 USC00215012, at 47.3169, -95.9692, elevation 369 m (1,212 ft).
- Data quality: Representative (10+ years), 15 years of freeze data.
- Average days per year at or below 32°F: 185.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Fosston 1 E (33 km)
- Ada (41 km)
- Tamarac Wildlife Re (46 km)
- Detroit Lakes 1 NNE (54 km)
- Detroit Lakes 12e (58 km)
- Itasca Univ Of Minn (60 km)
- Georgetown 1 E (66 km)
- Red Lake Falls (67 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.