Last spring frost
May 7
Frost Dates for Mackinaw City, MI
First fall frost
Oct 23
Growing season
167 days
Hardiness zone
5b
In an average year around Mackinaw City, MI, the last spring frost (32°F) is about May 7 and the first fall frost is about Oct 23, giving roughly a 167-day growing season. To be safe most years, wait until Apr 25 before setting out tender plants.
Last spring frost
Dates the last frost of spring typically ends. Plant tender crops after the risk has passed for your comfort level.
| Frost intensity | Early (10%) | Average (50%) | Late (90%) |
|---|---|---|---|
| Light (36°F) | Jun 2 | May 20 | May 6 |
| Freeze (32°F) | May 22 | May 7 | Apr 25 |
| Hard (28°F) | May 10 | Apr 25 | Apr 11 |
| Severe (24°F) | Apr 28 | Apr 13 | Apr 1 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Jun 2 | May 28 | May 24 | May 22 | May 20 | May 17 | May 14 | May 10 | May 6 |
| 32°F | May 22 | May 17 | May 13 | May 10 | May 7 | May 4 | May 1 | Apr 28 | Apr 25 |
| 28°F | May 10 | May 4 | May 1 | Apr 28 | Apr 25 | Apr 22 | Apr 19 | Apr 16 | Apr 11 |
| 24°F | Apr 28 | Apr 22 | Apr 18 | Apr 16 | Apr 13 | Apr 10 | Apr 8 | Apr 5 | Apr 1 |
| 20°F | Apr 17 | Apr 12 | Apr 8 | Apr 6 | Apr 4 | Apr 3 | Apr 1 | Mar 29 | Mar 22 |
| 16°F | Apr 9 | Apr 6 | Apr 3 | Apr 1 | Mar 31 | Mar 27 | Mar 24 | Mar 20 | Mar 16 |
First fall frost
Dates the first frost of fall typically arrives. Count back by a crop's days-to-maturity to know your planting cutoff.
| Frost intensity | Early (10%) | Average (50%) | Late (90%) |
|---|---|---|---|
| Light (36°F) | Sep 28 | Oct 9 | Oct 25 |
| Freeze (32°F) | Oct 6 | Oct 23 | Nov 6 |
| Hard (28°F) | Oct 21 | Nov 3 | Nov 18 |
| Severe (24°F) | Nov 2 | Nov 15 | Nov 29 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 28 | Oct 1 | Oct 4 | Oct 7 | Oct 9 | Oct 12 | Oct 15 | Oct 19 | Oct 25 |
| 32°F | Oct 6 | Oct 12 | Oct 16 | Oct 20 | Oct 23 | Oct 26 | Oct 30 | Nov 1 | Nov 6 |
| 28°F | Oct 21 | Oct 26 | Oct 30 | Nov 1 | Nov 3 | Nov 6 | Nov 9 | Nov 13 | Nov 18 |
| 24°F | Nov 2 | Nov 5 | Nov 8 | Nov 12 | Nov 15 | Nov 18 | Nov 20 | Nov 24 | Nov 29 |
| 20°F | Nov 9 | Nov 15 | Nov 18 | Nov 21 | Nov 24 | Nov 27 | Nov 30 | Dec 4 | Dec 10 |
| 16°F | Nov 17 | Nov 22 | Nov 26 | Nov 29 | Dec 2 | Dec 6 | Dec 10 | Dec 15 | Dec 21 |
Growing season is measured at 32°F with about 50% probability. Hardiness zone from the 2023 USDA map; frost normals from NOAA 1991-2020.
Where this data comes from
@endif These dates are computed from the nearest official weather station with long-term records: St Ignace Mackinac Br, Mi, about 7.5 miles away@if(!empty($station['elevation_ft'])), at 595 ft elevation. The further the station and the greater the elevation difference from your yard, the more your local frost timing can vary.
How we calculate these dates
Frost and freeze dates come from the NOAA 1991–2020 U.S. Climate Normals, the National Oceanic and Atmospheric Administration's 30-year averages for each weather station. A date shown at the 50% level is the median: in half of years the frost falls on or before it. The 10% and 90% columns show the early and late ends of the range, so you can plant on the odds you're comfortable with. These are long-term averages, not a forecast for this year - always check your local outlook before planting.
Source: NOAA National Centers for Environmental Information, 1991–2020 Climate Normals (public domain). Harman is not affiliated with or endorsed by NOAA.
Frequently asked questions
When is the last frost in Mackinaw City, MI?
On average, the last spring frost (32°F) around Mackinaw City, MI is about May 7. In cooler years it can run later, so for a safer bet many gardeners wait until Apr 25.
When is the first frost in the fall?
The first fall frost around Mackinaw City, MI typically arrives about Oct 23. Count back by a crop's days to maturity to find the latest date you can plant it.
When can I plant tomatoes and other tender crops?
Tender crops like tomatoes, peppers and basil are damaged by frost, so wait until the last spring frost has passed - around May 7 on average, or Apr 25 to be safe most years.
How long is the growing season here?
The frost-free growing season (between the last spring and first fall 32°F frost) is about 167 days in a typical year.
Are these dates a forecast for this year?
No. They are 30-year averages from the NOAA 1991–2020 Climate Normals, not a prediction for the current year. Use them for planning and always check your local weather forecast before planting or protecting crops.
Local weather for 49701 Planting calendar → Michigan frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026