Last spring frost
May 24
Frost Dates for Dunbar, WI
First fall frost
Sep 30
Growing season
128 days
Hardiness zone
4b
In an average year around Dunbar, WI, the last spring frost (32°F) is about May 24 and the first fall frost is about Sep 30, giving roughly a 128-day growing season. To be safe most years, wait until May 10 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 25 | Jun 5 | May 23 |
| Freeze (32°F) | Jun 7 | May 24 | May 10 |
| Hard (28°F) | May 26 | May 10 | Apr 26 |
| Severe (24°F) | May 13 | Apr 28 | Apr 14 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Jun 25 | Jun 16 | Jun 11 | Jun 8 | Jun 5 | Jun 2 | May 31 | May 27 | May 23 |
| 32°F | Jun 7 | Jun 2 | May 31 | May 27 | May 24 | May 21 | May 18 | May 15 | May 10 |
| 28°F | May 26 | May 21 | May 17 | May 14 | May 10 | May 7 | May 4 | Apr 30 | Apr 26 |
| 24°F | May 13 | May 8 | May 4 | Apr 30 | Apr 28 | Apr 26 | Apr 23 | Apr 19 | Apr 14 |
| 20°F | May 1 | Apr 27 | Apr 23 | Apr 20 | Apr 16 | Apr 13 | Apr 10 | Apr 7 | Apr 3 |
| 16°F | Apr 20 | Apr 15 | Apr 11 | Apr 8 | Apr 6 | Apr 3 | Apr 1 | Mar 30 | Mar 24 |
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 19 | Oct 1 |
| Freeze (32°F) | Sep 16 | Sep 30 | Oct 12 |
| Hard (28°F) | Sep 27 | Oct 10 | Oct 26 |
| Severe (24°F) | Oct 8 | Oct 24 | Nov 6 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 1 | Sep 7 | Sep 12 | Sep 16 | Sep 19 | Sep 21 | Sep 24 | Sep 28 | Oct 1 |
| 32°F | Sep 16 | Sep 20 | Sep 24 | Sep 27 | Sep 30 | Oct 2 | Oct 5 | Oct 8 | Oct 12 |
| 28°F | Sep 27 | Oct 1 | Oct 4 | Oct 7 | Oct 10 | Oct 13 | Oct 16 | Oct 20 | Oct 26 |
| 24°F | Oct 8 | Oct 13 | Oct 16 | Oct 20 | Oct 24 | Oct 26 | Oct 30 | Nov 2 | Nov 6 |
| 20°F | Oct 20 | Oct 27 | Oct 30 | Nov 1 | Nov 3 | Nov 5 | Nov 8 | Nov 12 | Nov 17 |
| 16°F | Nov 1 | Nov 3 | Nov 6 | Nov 9 | Nov 12 | Nov 14 | Nov 18 | Nov 21 | Nov 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: Goodman Sanitary Dist, Wi, about 8 miles away@if(!empty($station['elevation_ft'])), at 1,448 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 Dunbar, WI?
On average, the last spring frost (32°F) around Dunbar, WI is about May 24. In cooler years it can run later, so for a safer bet many gardeners wait until May 10.
When is the first frost in the fall?
The first fall frost around Dunbar, WI typically arrives about Sep 30. 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 24 on average, or May 10 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 128 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 54119 Planting calendar → Wisconsin frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026