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Frost Dates in Michigan
First and last frost dates across Michigan, computed from 93 NOAA weather stations (1991–2020 climate normals). Your exact date depends on your city and microclimate — use the ZIP lookup on the main tool for a station-specific answer.
Last spring frost
May 8
statewide median · range Apr 17–Jun 7
First fall frost
Oct 12
statewide median · range Sep 9–Nov 5
Growing season
155 days
median · range 94–201
Stations used
93
NOAA 1991–2020 normals
Frost dates by city
Median dates from the nearest NOAA station to each city. The "cautious" date is the 10% spring value — planting after it means only a ~10% chance of a later frost.
| City | Nearest station | Last spring frost | First fall frost | Growing season | Safe transplant |
|---|---|---|---|---|---|
| Detroit | Detroit City Ap · 6 mi | Apr 21 (cautious: May 6) | Oct 31 | 190 days | May 5 |
| Grand Rapids | Grand Rapids · 8 mi | Apr 29 (cautious: May 15) | Oct 20 | 174 days | May 13 |
| Ann Arbor | Ann Arbor U Of Mich · 4 mi | May 3 (cautious: May 20) | Oct 13 | 160 days | May 17 |
How frost varies across Michigan
Spring frost timing spans about 51 days across the state. S Haven in southern Michigan typically sees its last spring frost around April 17, while Vanderbilt in eastern Michigan doesn't clear frost until about June 7. Within any city, low spots and valleys run colder than the station average; areas near buildings and pavement run warmer.
When to plant in Michigan
As a rule of thumb, cool-season crops (lettuce, peas, spinach) can go in 2–4 weeks before your last spring frost; warm-season transplants (tomatoes, peppers) should wait about 2 weeks after it — around May 22 for the statewide median. Check your city's row above rather than the statewide median: a 51-day statewide spread makes the city-level date the one that matters.
These are climate normals (what's typical), not forecasts. For the current year, watch the 10-day forecast around your planting date.
How this is computed
Statewide medians are the median of the 93 NOAA stations' median frost dates — half the stations run earlier, half later. City rows use the nearest station with 30-year freeze records. Dates are 32°F freeze probabilities from NOAA NCEI 1991–2020 U.S. Climate Normals; nothing is estimated or interpolated.
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Frequently asked questions
When is the last frost date in Michigan?
The statewide median last spring frost is May 8, but it ranges from April 17 to June 7 depending on where in the state you are. Use your city's row in the table above, or the ZIP lookup on the main tool, for a station-specific date.
When can I plant tomatoes outside in Michigan?
Warm-season transplants like tomatoes should wait about two weeks after your last spring frost — around May 22 for the statewide median. Your city may differ by weeks; check the "safe transplant" column in the city table.
How long is the growing season in Michigan?
The median growing season across 93 NOAA stations is 155 days, ranging from 94 to 201 days by location.
Why do frost dates vary so much within Michigan?
Frost timing follows latitude, elevation, and local terrain. Across Michigan, last spring frost dates span about 51 days — from around April 17 near S Haven to June 7 near Vanderbilt. Microclimates (low spots, valleys, urban heat) shift dates further at the garden level.
Where does this data come from?
All frost dates are computed from the NOAA National Centers for Environmental Information 1991–2020 U.S. Climate Normals freeze data (public domain), using each station's 32°F freeze probability statistics. No dates are estimated or interpolated.