Last spring frost
May 9
Frost Dates for Sault Ste. Marie, MI
First fall frost
Oct 11
Growing season
151 days
Hardiness zone
4b
In an average year around Sault Ste. Marie, MI, the last spring frost (32°F) is about May 9 and the first fall frost is about Oct 11, giving roughly a 151-day growing season. To be safe most years, wait until Apr 27 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 11 | May 26 | May 10 |
| Freeze (32°F) | May 27 | May 9 | Apr 27 |
| Hard (28°F) | May 10 | Apr 27 | Apr 14 |
| Severe (24°F) | Apr 26 | Apr 14 | Apr 3 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Jun 11 | Jun 5 | Jun 1 | May 30 | May 26 | May 23 | May 21 | May 17 | May 10 |
| 32°F | May 27 | May 21 | May 17 | May 13 | May 9 | May 6 | May 2 | Apr 30 | Apr 27 |
| 28°F | May 10 | May 4 | May 1 | Apr 29 | Apr 27 | Apr 24 | Apr 21 | Apr 18 | Apr 14 |
| 24°F | Apr 26 | Apr 22 | Apr 19 | Apr 16 | Apr 14 | Apr 12 | Apr 9 | Apr 6 | Apr 3 |
| 20°F | Apr 19 | Apr 15 | Apr 12 | Apr 9 | Apr 7 | Apr 5 | Apr 2 | Apr 1 | Mar 27 |
| 16°F | Apr 13 | Apr 9 | Apr 5 | Apr 3 | Apr 1 | Mar 31 | Mar 28 | Mar 24 | Mar 19 |
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 15 | Sep 29 | Oct 12 |
| Freeze (32°F) | Sep 26 | Oct 11 | Oct 26 |
| Hard (28°F) | Oct 8 | Oct 26 | Nov 9 |
| Severe (24°F) | Oct 24 | Nov 6 | Nov 20 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 15 | Sep 20 | Sep 23 | Sep 27 | Sep 29 | Oct 2 | Oct 4 | Oct 7 | Oct 12 |
| 32°F | Sep 26 | Oct 1 | Oct 5 | Oct 7 | Oct 11 | Oct 13 | Oct 16 | Oct 20 | Oct 26 |
| 28°F | Oct 8 | Oct 14 | Oct 18 | Oct 22 | Oct 26 | Oct 29 | Nov 1 | Nov 4 | Nov 9 |
| 24°F | Oct 24 | Oct 29 | Nov 1 | Nov 4 | Nov 6 | Nov 9 | Nov 12 | Nov 15 | Nov 20 |
| 20°F | Nov 3 | Nov 7 | Nov 10 | Nov 13 | Nov 15 | Nov 18 | Nov 20 | Nov 24 | Nov 28 |
| 16°F | Nov 9 | Nov 13 | Nov 16 | Nov 19 | Nov 21 | Nov 25 | Nov 28 | Dec 1 | Dec 6 |
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: Sault Ste Marie Sanderson Fld, Mi, about 5.4 miles away@if(!empty($station['elevation_ft'])), at 722 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 Sault Ste. Marie, MI?
On average, the last spring frost (32°F) around Sault Ste. Marie, MI is about May 9. In cooler years it can run later, so for a safer bet many gardeners wait until Apr 27.
When is the first frost in the fall?
The first fall frost around Sault Ste. Marie, MI typically arrives about Oct 11. 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 9 on average, or Apr 27 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 151 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 49783 Planting calendar → Michigan frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026