Frost dates for Grand Marais, MN
At Grand Marais, the median last spring frost (32°F) is May 20 and the median first fall frost is Oct 5, for a typical growing season of 137 days. For a 90% chance that the last frost has passed, wait until Jun 6. Nearby ZIP codes are in USDA hardiness zones 3b to 4b.
- May 20Last spring frost (median)50% chance of 32°F after this date
- Jun 6Safer planting date10% chance of 32°F after this date
- Oct 5First fall frost (median)50% chance of 32°F by this date
- 137 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 19 | Jun 2 | Jun 18 |
| 32°F | May 3 | May 20 | Jun 6 |
| 28°F | Apr 21 | May 4 | May 20 |
| 24°F | Apr 8 | Apr 23 | May 6 |
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 12 | Sep 26 | Oct 8 |
| 32°F | Sep 22 | Oct 5 | Oct 20 |
| 28°F | Oct 1 | Oct 17 | Nov 1 |
| 24°F | Oct 15 | Oct 30 | 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 | 94 days | 114 days | 134 days |
| 32°F | 113 days | 137 days | 159 days |
| 28°F | 141 days | 163 days | 184 days |
| 24°F | 168 days | 189 days | 208 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 | 28 km |
| 55604 | 3b | -35 to -30°F | 32 km |
| 55606 | 4a | -30 to -25°F | 33 km |
| 55615 | 3b | -35 to -30°F | 39 km |
| 55613 | 4b | -25 to -20°F | 53 km |
| 55605 | 4b | -25 to -20°F | 55 km |
| 55603 | 4a | -30 to -25°F | 69 km |
| 55607 | 3b | -35 to -30°F | 89 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 USC00213282, at 47.7517, -90.3283, elevation 186 m (612 ft).
- Data quality: Standard (24+ years of data), 28 years of freeze data.
- Average days per year at or below 32°F: 178.
- 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 (26 km)
- Grand Portage (53 km)
- Gunflint Lake 10 NW (61 km)
- Wolf Ridge Elc (75 km)
- Ely 25e (87 km)
- Isabella 14w (101 km)
- Ely (113 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.