Last spring frost
May 27
Frost Dates for Grand Marais, MI
First fall frost
Oct 10
Growing season
138 days
Hardiness zone
5a
In an average year around Grand Marais, MI, the last spring frost (32°F) is about May 27 and the first fall frost is about Oct 10, giving roughly a 138-day growing season. To be safe most years, wait until May 7 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) | Jul 6 | Jun 10 | May 26 |
| Freeze (32°F) | Jun 13 | May 27 | May 7 |
| Hard (28°F) | May 27 | May 9 | Apr 25 |
| Severe (24°F) | May 11 | Apr 26 | Apr 12 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Jul 6 | Jun 24 | Jun 18 | Jun 13 | Jun 10 | Jun 6 | Jun 3 | May 31 | May 26 |
| 32°F | Jun 13 | Jun 6 | Jun 2 | May 30 | May 27 | May 24 | May 20 | May 15 | May 7 |
| 28°F | May 27 | May 21 | May 17 | May 12 | May 9 | May 5 | May 2 | Apr 29 | Apr 25 |
| 24°F | May 11 | May 5 | May 2 | Apr 29 | Apr 26 | Apr 24 | Apr 20 | Apr 17 | Apr 12 |
| 20°F | Apr 30 | Apr 25 | Apr 22 | Apr 19 | Apr 16 | Apr 13 | Apr 10 | Apr 7 | Apr 2 |
| 16°F | Apr 21 | Apr 17 | Apr 13 | Apr 9 | Apr 6 | Apr 3 | Apr 1 | Mar 29 | Mar 22 |
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 5 | Sep 29 | Oct 12 |
| Freeze (32°F) | Sep 25 | Oct 10 | Oct 27 |
| Hard (28°F) | Oct 7 | Oct 25 | Nov 8 |
| Severe (24°F) | Oct 23 | Nov 5 | Nov 20 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 5 | Sep 16 | Sep 22 | Sep 26 | Sep 29 | Oct 2 | Oct 5 | Oct 8 | Oct 12 |
| 32°F | Sep 25 | Oct 1 | Oct 4 | Oct 7 | Oct 10 | Oct 13 | Oct 17 | Oct 20 | Oct 27 |
| 28°F | Oct 7 | Oct 13 | Oct 18 | Oct 22 | Oct 25 | Oct 29 | Nov 1 | Nov 3 | Nov 8 |
| 24°F | Oct 23 | Oct 28 | Nov 1 | Nov 3 | Nov 5 | Nov 8 | Nov 11 | Nov 15 | Nov 20 |
| 20°F | Nov 2 | Nov 5 | Nov 10 | Nov 13 | Nov 15 | Nov 18 | Nov 21 | Nov 25 | Dec 1 |
| 16°F | Nov 10 | Nov 15 | Nov 19 | Nov 22 | Nov 25 | Nov 28 | Dec 1 | Dec 5 | Dec 11 |
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: Grand Marais 2 E, Mi, about 17.9 miles away@if(!empty($station['elevation_ft'])), at 624 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 Grand Marais, MI?
On average, the last spring frost (32°F) around Grand Marais, MI is about May 27. In cooler years it can run later, so for a safer bet many gardeners wait until May 7.
When is the first frost in the fall?
The first fall frost around Grand Marais, MI typically arrives about Oct 10. 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 27 on average, or May 7 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 138 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 49883 Planting calendar → Michigan frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026