Frost dates for Two Harbors, MN
At Two Harbors, the median last spring frost (32°F) is May 12 and the median first fall frost is Oct 6, for a typical growing season of 145 days. For a 90% chance that the last frost has passed, wait until May 30. Nearby ZIP codes are in USDA hardiness zone 4b.
- May 12Last spring frost (median)50% chance of 32°F after this date
- May 30Safer planting date10% chance of 32°F after this date
- Oct 6First fall frost (median)50% chance of 32°F by this date
- 145 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 14 | May 28 | Jun 11 |
| 32°F | Apr 30 | May 12 | May 30 |
| 28°F | Apr 16 | Apr 29 | May 11 |
| 24°F | Apr 4 | Apr 16 | Apr 28 |
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 13 | Sep 27 | Oct 10 |
| 32°F | Sep 19 | Oct 6 | Oct 21 |
| 28°F | Oct 1 | Oct 20 | Nov 4 |
| 24°F | Oct 19 | Nov 2 | Nov 15 |
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 | 101 days | 120 days | 139 days |
| 32°F | 122 days | 145 days | 167 days |
| 28°F | 151 days | 174 days | 196 days |
| 24°F | 180 days | 200 days | 218 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 |
|---|---|---|---|
| 55609 | 4b | -25 to -20°F | 11 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 USC00218419, at 47.0258, -91.6653, elevation 190 m (625 ft).
- Data quality: Standard (24+ years of data), 30 years of freeze data.
- Average days per year at or below 32°F: 164.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Two Harbors 7nw (11 km)
- Brimson 2s (29 km)
- Island Lake 4e (31 km)
- Duluth Harbor Station (43 km)
- Duluth (46 km)
- Duluth NWS (46 km)
- Wolf Ridge Elc (58 km)
- Cotton (62 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.