Michigan's last frost date is the single most important number in your gardening year. Everything — from when you start seeds indoors to when you transplant tomatoes — flows from this date. It varies by up to 6 weeks across the state.
| City | Zone | Avg Last Frost | Safe Transplant Date | First Fall Frost |
|---|---|---|---|---|
| Detroit / Metro area | 6b | April 15–22 | May 1–7 | Oct 20–27 |
| Ann Arbor | 6a | April 20–27 | May 5–10 | Oct 15–22 |
| Grand Rapids | 6a | April 25 – May 3 | May 10–15 | Oct 12–18 |
| Lansing | 6a | May 1–8 | May 12–18 | Oct 8–14 |
| Flint | 6a | April 28 – May 5 | May 10–15 | Oct 10–16 |
| Muskegon | 6a | April 22–29 | May 7–12 | Oct 18–24 |
| Kalamazoo | 5b/6a | April 28 – May 5 | May 10–15 | Oct 12–18 |
| Benton Harbor | 6b | April 14–20 | Apr 28 – May 5 | Oct 22–28 |
| Holland | 6b | April 20–26 | May 5–10 | Oct 20–26 |
| Traverse City | 5b/6a | May 5–12 | May 18–24 | Oct 5–12 |
| Alpena | 5b | May 10–17 | May 22–28 | Sept 30 – Oct 7 |
| Cadillac | 5b | May 8–15 | May 20–26 | Oct 3–10 |
| Bay City / Saginaw | 6a | April 30 – May 7 | May 12–18 | Oct 10–17 |
| Gaylord | 5a | May 15–22 | May 28 – June 4 | Sept 24 – Oct 1 |
| Marquette | 5b | May 12–19 | May 25–31 | Oct 1–8 |
| Sault Ste. Marie | 5a | May 15–23 | May 28 – June 5 | Sept 22–29 |
| Ironwood | 4b | May 20–28 | June 3–10 | Sept 15–22 |
| Iron River | 4a | May 22–30 | June 5–12 | Sept 12–19 |
Cities within 20 miles of Lake Michigan often have later last frost dates in spring — despite being in warmer zones. Cold lake water keeps April and May temperatures lower near shore, even as inland areas warm up. This is the "spring delay" effect.