Last spring frost
May 19
Frost Dates for Boon, MI
First fall frost
Oct 1
Growing season
135 days
Hardiness zone
5a
In an average year around Boon, MI, the last spring frost (32°F) is about May 19 and the first fall frost is about Oct 1, giving roughly a 135-day growing season. To be safe most years, wait until May 2 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 14 | May 31 | May 16 |
| Freeze (32°F) | Jun 3 | May 19 | May 2 |
| Hard (28°F) | May 21 | May 5 | Apr 21 |
| Severe (24°F) | May 10 | Apr 23 | Apr 8 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Jun 14 | Jun 9 | Jun 5 | Jun 2 | May 31 | May 28 | May 24 | May 21 | May 16 |
| 32°F | Jun 3 | May 29 | May 24 | May 22 | May 19 | May 16 | May 11 | May 7 | May 2 |
| 28°F | May 21 | May 16 | May 12 | May 8 | May 5 | May 2 | Apr 29 | Apr 25 | Apr 21 |
| 24°F | May 10 | May 3 | Apr 29 | Apr 26 | Apr 23 | Apr 20 | Apr 17 | Apr 13 | Apr 8 |
| 20°F | Apr 26 | Apr 20 | Apr 17 | Apr 14 | Apr 11 | Apr 8 | Apr 5 | Apr 2 | Mar 28 |
| 16°F | Apr 15 | Apr 10 | Apr 7 | Apr 4 | Apr 2 | Mar 31 | Mar 28 | Mar 23 | Mar 18 |
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) | Aug 31 | Sep 20 | Oct 4 |
| Freeze (32°F) | Sep 17 | Oct 1 | Oct 16 |
| Hard (28°F) | Sep 28 | Oct 13 | Oct 31 |
| Severe (24°F) | Oct 10 | Oct 30 | Nov 14 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Aug 31 | Sep 8 | Sep 13 | Sep 17 | Sep 20 | Sep 23 | Sep 26 | Sep 30 | Oct 4 |
| 32°F | Sep 17 | Sep 22 | Sep 25 | Sep 29 | Oct 1 | Oct 4 | Oct 7 | Oct 11 | Oct 16 |
| 28°F | Sep 28 | Oct 3 | Oct 6 | Oct 10 | Oct 13 | Oct 17 | Oct 21 | Oct 26 | Oct 31 |
| 24°F | Oct 10 | Oct 17 | Oct 22 | Oct 26 | Oct 30 | Nov 1 | Nov 5 | Nov 9 | Nov 14 |
| 20°F | Oct 29 | Nov 2 | Nov 5 | Nov 9 | Nov 12 | Nov 15 | Nov 18 | Nov 21 | Nov 28 |
| 16°F | Nov 6 | Nov 12 | Nov 16 | Nov 19 | Nov 22 | Nov 25 | Nov 29 | Dec 3 | Dec 8 |
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: Cadillac, Mi, about 9.9 miles away@if(!empty($station['elevation_ft'])), at 1,295 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 Boon, MI?
On average, the last spring frost (32°F) around Boon, MI is about May 19. In cooler years it can run later, so for a safer bet many gardeners wait until May 2.
When is the first frost in the fall?
The first fall frost around Boon, MI typically arrives about Oct 1. 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 19 on average, or May 2 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 135 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 49618 Planting calendar → Michigan frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026