Frost Dates for Ann Arbor, MI
In Ann Arbor, MI, the average last spring frost is around May 5 and the average first fall frost around Oct 10, for a growing season of about 157 days. For frost-tender plants, wait until May 20, when the chance of frost drops to 10%.
Based on NOAA 1991–2020 records from the Ann Arbor Se, MI weather station, 3 miles away, elevation 832 ft. Frost can come earlier in low spots and valleys and later near cities and large lakes.
Frost probability by date
Chance of a 32°F frost after the spring date, or before the fall date.
| Chance | Last spring frost | First fall frost |
|---|---|---|
| 10% | May 20 | Sep 28 |
| 20% | May 15 | Oct 1 |
| 30% | May 11 | Oct 4 |
| 40% | May 8 | Oct 7 |
| 50% | May 5 | Oct 10 |
| 60% | May 2 | Oct 13 |
| 70% | Apr 30 | Oct 16 |
| 80% | Apr 26 | Oct 20 |
| 90% | Apr 21 | Oct 24 |
Light frost vs. hard freeze
Average (50%) dates for each temperature. Tender plants are damaged at 36°F; most hardy crops survive until 28°F.
| Temperature | Last in spring | First in fall |
|---|---|---|
| Light frost (36°F) | May 15 | Oct 1 |
| Frost / freeze (32°F) | May 5 | Oct 10 |
| Hard freeze (28°F) | Apr 24 | Oct 23 |
Planting calendar for Ann Arbor
Transplant May 12 – May 26
Transplant May 19 – Jun 2
Transplant May 19 – Jun 2
Transplant May 12 – May 26
Sow or transplant May 12 – May 26
Sow or transplant May 12 – May 26
Sow or transplant May 19 – Jun 2
Sow or transplant Apr 7 – Apr 21
Fall sowing Aug 15 – Sep 12
Fall sowing Aug 15 – Sep 5
Fall sowing Aug 1 – Aug 15
Sow or transplant Apr 7 – Apr 21
Fall sowing Aug 1 – Aug 29
Transplant Apr 21 – May 5
Fall sowing Jul 18 – Aug 1
Transplant Apr 14 – Apr 28
Fall sowing Jul 18 – Aug 1
Fall sowing Jul 18 – Aug 1
Fall sowing Aug 29 – Sep 19
Fall sowing Aug 1 – Aug 15
Plant Apr 7 – Apr 21
Based on the average last frost (May 5) and first frost (Oct 10). The dashed lines mark those dates. Seed packets list days to maturity; adjust for your varieties.