Frost dates for Iron Mtn-Kingsford Wastewater Plant, MI
At Iron Mtn-Kingsford Wastewater Plant, the median last spring frost (32°F) is May 17 and the median first fall frost is Oct 1, for a typical growing season of 135 days. For a 90% chance that the last frost has passed, wait until May 31. Nearby ZIP codes are in USDA hardiness zones 4b to 5a.
- May 17Last spring frost (median)50% chance of 32°F after this date
- May 31Safer planting date10% chance of 32°F after this date
- Oct 1First fall frost (median)50% chance of 32°F by this date
- 135 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 15 | May 29 | Jun 12 |
| 32°F | May 2 | May 17 | May 31 |
| 28°F | Apr 24 | May 4 | May 19 |
| 24°F | Apr 11 | Apr 24 | May 9 |
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 6 | Sep 21 | Oct 4 |
| 32°F | Sep 17 | Oct 1 | Oct 13 |
| 28°F | Sep 27 | Oct 11 | Oct 27 |
| 24°F | Oct 7 | Oct 24 | Nov 8 |
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 | 97 days | 115 days | 132 days |
| 32°F | 118 days | 135 days | 153 days |
| 28°F | 136 days | 157 days | 176 days |
| 24°F | 159 days | 180 days | 201 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 |
|---|---|---|---|
| 49802 | 4b | -25 to -20°F | 2 km |
| 49876 | 4b | -25 to -20°F | 8 km |
| 54151 | 4b | -25 to -20°F | 10 km |
| 49870 | 4b | -25 to -20°F | 18 km |
| 49852 | 5a | -20 to -15°F | 21 km |
| 54156 | 4b | -25 to -20°F | 22 km |
| 49892 | 5a | -20 to -15°F | 23 km |
| 49834 | 4b | -25 to -20°F | 36 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 USC00204090, at 45.7858, -88.0842, elevation 326 m (1,071 ft).
- Data quality: Standard (24+ years of data), 28 years of freeze data.
- Average days per year at or below 32°F: 182.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Iron Mountain Ford Airport (4 km)
- Stambaugh 2sse (52 km)
- Stephenson 5wsw (53 km)
- Amasa 1w (58 km)
- Cornell 5se (72 km)
- Escanaba (77 km)
- Clarksburg (81 km)
- Ki Sawyer Wastewater Plant (82 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.