Frost dates for Alpena Co Regional Airport, MI
At Alpena Co Regional Airport, 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 136 days. For a 90% chance that the last frost has passed, wait until May 31. Nearby ZIP codes are in USDA hardiness zone 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
- 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 15 | May 29 | Jun 12 |
| 32°F | May 1 | May 17 | May 31 |
| 28°F | Apr 20 | May 4 | May 19 |
| 24°F | Apr 8 | Apr 23 | May 7 |
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 4 | Sep 21 | Oct 3 |
| 32°F | Sep 18 | Oct 1 | Oct 16 |
| 28°F | Sep 29 | Oct 15 | Oct 31 |
| 24°F | Oct 13 | 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 | 91 days | 112 days | 131 days |
| 32°F | 115 days | 136 days | 157 days |
| 28°F | 140 days | 162 days | 184 days |
| 24°F | 165 days | 189 days | 210 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 |
|---|---|---|---|
| 49744 | 5a | -20 to -15°F | 11 km |
| 49753 | 5a | -20 to -15°F | 18 km |
| 49747 | 5a | -20 to -15°F | 27 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 USW00094849, at 45.0717, -83.5644, elevation 208 m (684 ft).
- Data quality: Standard (24+ years of data), 30 years of freeze data.
- Average days per year at or below 32°F: 169.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Alpena 10nw (10 km)
- Alpena Wastewater Plant (11 km)
- Rogers City (43 km)
- Atlanta (46 km)
- Harrisville 2nne (49 km)
- Atlanta 5 WNW (53 km)
- Glennie 2se (61 km)
- Mio Hydro Plant (64 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.