Frost dates for Grand Marais, MN
At Grand Marais, the median last spring frost (32°F) is May 22 and the median first fall frost is Oct 9, for a typical growing season of 136 days. For a 90% chance that the last frost has passed, wait until Jun 18. Nearby ZIP codes are in USDA hardiness zones 3b to 4b.
- May 22Last spring frost (median)50% chance of 32°F after this date
- Jun 18Safer planting date10% chance of 32°F after this date
- Oct 9First fall frost (median)50% chance of 32°F by this date
- 136 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 17 | Jun 3 | Jun 30 |
| 32°F | May 3 | May 22 | Jun 18 |
| 28°F | Apr 19 | May 4 | Jun 8 |
| 24°F | Apr 4 | Apr 20 | May 13 |
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 29 | Oct 11 |
| 32°F | Sep 25 | Oct 9 | Oct 25 |
| 28°F | Oct 6 | Oct 24 | Nov 8 |
| 24°F | Oct 22 | Nov 4 | Nov 18 |
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 | 80 days | 112 days | 136 days |
| 32°F | 109 days | 136 days | 163 days |
| 28°F | 133 days | 167 days | 192 days |
| 24°F | 168 days | 197 days | 215 days |
Chance of a freeze in any year
| Temperature | Chance per year |
|---|---|
| 36°F | 100% |
| 32°F | 100% |
| 28°F | 100% |
| 24°F | 100% |
Closest ZIP codes (each is closer to another station)
| ZIP | Hardiness zone | Avg. extreme low | Distance |
|---|---|---|---|
| 55612 | 3b | -35 to -30°F | 27 km |
| 55604 | 3b | -35 to -30°F | 32 km |
| 55606 | 4a | -30 to -25°F | 34 km |
| 55615 | 3b | -35 to -30°F | 38 km |
| 55613 | 4b | -25 to -20°F | 52 km |
| 55605 | 4b | -25 to -20°F | 56 km |
| 55603 | 4a | -30 to -25°F | 68 km |
| 55607 | 3b | -35 to -30°F | 88 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 USW00094992, at 47.7472, -90.3444, elevation 186 m (610 ft).
- Data quality: Representative (10+ years), 22 years of freeze data.
- Average days per year at or below 32°F: 170.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Grand Marais (1 km)
- Lutsen 3nne (25 km)
- Grand Portage (55 km)
- Gunflint Lake 10 NW (61 km)
- Wolf Ridge Elc (73 km)
- Ely 25e (86 km)
- Isabella 14w (99 km)
- Ely (112 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.