Last spring frost
May 19
Frost Dates for Rothbury, MI
First fall frost
Oct 4
Growing season
136 days
Hardiness zone
6a
In an average year around Rothbury, MI, the last spring frost (32°F) is about May 19 and the first fall frost is about Oct 4, giving roughly a 136-day growing season. To be safe most years, wait until May 1 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 22 | May 31 | May 15 |
| Freeze (32°F) | Jun 6 | May 19 | May 1 |
| Hard (28°F) | May 26 | May 5 | Apr 19 |
| Severe (24°F) | May 10 | Apr 21 | Apr 5 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Jun 22 | Jun 12 | Jun 7 | Jun 3 | May 31 | May 28 | May 25 | May 22 | May 15 |
| 32°F | Jun 6 | May 31 | May 27 | May 23 | May 19 | May 15 | May 11 | May 7 | May 1 |
| 28°F | May 26 | May 18 | May 13 | May 9 | May 5 | May 1 | Apr 29 | Apr 25 | Apr 19 |
| 24°F | May 10 | May 3 | Apr 28 | Apr 25 | Apr 21 | Apr 18 | Apr 14 | Apr 10 | Apr 5 |
| 20°F | Apr 24 | Apr 19 | Apr 16 | Apr 12 | Apr 8 | Apr 5 | Apr 2 | Mar 30 | Mar 24 |
| 16°F | Apr 11 | Apr 5 | Apr 2 | Mar 31 | Mar 28 | Mar 24 | Mar 21 | Mar 17 | Mar 11 |
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 1 | Sep 23 | Oct 7 |
| Freeze (32°F) | Sep 16 | Oct 4 | Oct 20 |
| Hard (28°F) | Sep 30 | Oct 18 | Nov 4 |
| Severe (24°F) | Oct 16 | Nov 2 | Nov 22 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 1 | Sep 9 | Sep 13 | Sep 18 | Sep 23 | Sep 27 | Oct 1 | Oct 3 | Oct 7 |
| 32°F | Sep 16 | Sep 22 | Sep 27 | Oct 1 | Oct 4 | Oct 7 | Oct 10 | Oct 15 | Oct 20 |
| 28°F | Sep 30 | Oct 5 | Oct 10 | Oct 14 | Oct 18 | Oct 21 | Oct 25 | Oct 30 | Nov 4 |
| 24°F | Oct 16 | Oct 23 | Oct 28 | Nov 1 | Nov 2 | Nov 6 | Nov 9 | Nov 15 | Nov 22 |
| 20°F | Nov 1 | Nov 6 | Nov 11 | Nov 16 | Nov 20 | Nov 24 | Nov 28 | Dec 2 | Dec 8 |
| 16°F | Nov 16 | Nov 23 | Nov 28 | Dec 2 | Dec 5 | Dec 9 | Dec 14 | Dec 20 | Dec 26 |
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: Montague 4 Nw, Mi, about 8.9 miles away@if(!empty($station['elevation_ft'])), at 650 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 Rothbury, MI?
On average, the last spring frost (32°F) around Rothbury, MI is about May 19. In cooler years it can run later, so for a safer bet many gardeners wait until May 1.
When is the first frost in the fall?
The first fall frost around Rothbury, MI typically arrives about Oct 4. 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 1 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 136 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 49452 Planting calendar → Michigan frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026