Frost dates for Ann Arbor SE, MI
At Ann Arbor SE, the median last spring frost (32°F) is May 5 and the median first fall frost is Oct 10, for a typical growing season of 157 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 5Last spring frost (median)50% chance of 32°F after this date
- May 20Safer planting date10% chance of 32°F after this date
- Oct 10First fall frost (median)50% chance of 32°F by this date
- 157 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 1 | May 15 | May 29 |
| 32°F | Apr 21 | May 5 | May 20 |
| 28°F | Apr 10 | Apr 24 | May 11 |
| 24°F | Mar 31 | Apr 11 | Apr 27 |
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 18 | Oct 1 | Oct 12 |
| 32°F | Sep 28 | Oct 10 | Oct 24 |
| 28°F | Oct 7 | Oct 23 | Nov 6 |
| 24°F | Oct 22 | Nov 5 | Nov 18 |
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 | 117 days | 137 days | 157 days |
| 32°F | 138 days | 157 days | 176 days |
| 28°F | 160 days | 180 days | 199 days |
| 24°F | 186 days | 207 days | 226 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 |
|---|---|---|---|
| 48104 | 6a | -10 to -5°F | 3 km |
| 48197 | 6a | -10 to -5°F | 7 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 USC00200228, at 42.2417, -83.6933, elevation 254 m (832 ft).
- Data quality: Representative (10+ years), 17 years of freeze data.
- Average days per year at or below 32°F: 147.
- Frost risk changes over short distances. Valleys and low spots freeze earlier than hillsides and city centers.
Nearby weather stations
- Ann Arbor Muni Airport (5 km)
- Ann Arbor U Of Mich (7 km)
- Saline Wastewater Plant (12 km)
- Detroit Willow Run Airport (13 km)
- Saline 4sw (17 km)
- Milan Wastewater Plant (18 km)
- Milan 4 ESE (20 km)
- Whitmore Lake 1nw (23 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.