Frost dates for Ann Arbor U Of Mich, MI
At Ann Arbor U Of Mich, the median last spring frost (32°F) is May 3 and the median first fall frost is Oct 13, for a typical growing season of 160 days. For a 90% chance that the last frost has passed, wait until May 20. Nearby ZIP codes are in USDA hardiness zone 6a.
- May 3Last spring frost (median)50% chance of 32°F after this date
- May 20Safer planting date10% chance of 32°F after this date
- Oct 13First fall frost (median)50% chance of 32°F by this date
- 160 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 | Apr 30 | May 16 | May 31 |
| 32°F | Apr 20 | May 3 | May 20 |
| 28°F | Apr 9 | Apr 23 | May 9 |
| 24°F | Mar 30 | Apr 11 | Apr 26 |
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 20 | Oct 2 | Oct 14 |
| 32°F | Sep 29 | Oct 13 | Oct 27 |
| 28°F | Oct 12 | Oct 26 | Nov 8 |
| 24°F | Oct 25 | Nov 6 | Nov 20 |
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 | 119 days | 138 days | 157 days |
| 32°F | 138 days | 160 days | 179 days |
| 28°F | 162 days | 183 days | 203 days |
| 24°F | 187 days | 209 days | 229 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 |
|---|---|---|---|
| 48109 | 6a | -10 to -5°F | 4 km |
| 48105 | 6a | -10 to -5°F | 4 km |
| 48170 | 6a | -10 to -5°F | 13 km |
| 48168 | 6a | -10 to -5°F | 16 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 USC00200230, at 42.2981, -83.6639, elevation 248 m (813 ft).
- Data quality: Standard (24+ years of data), 29 years of freeze data.
- Average days per year at or below 32°F: 130.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Ann Arbor SE (7 km)
- Ann Arbor Muni Airport (11 km)
- Detroit Willow Run Airport (13 km)
- Saline Wastewater Plant (18 km)
- Whitmore Lake 1nw (18 km)
- Saline 4sw (23 km)
- Milan Wastewater Plant (24 km)
- Milan 4 ESE (26 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.