Last spring frost
May 23
Frost Dates for Birch Hill, WI
First fall frost
Oct 1
Growing season
132 days
Hardiness zone
4b
In an average year around Birch Hill, WI, the last spring frost (32°F) is about May 23 and the first fall frost is about Oct 1, giving roughly a 132-day growing season. To be safe most years, wait until May 4 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 18 | Jun 3 | May 21 |
| Freeze (32°F) | Jun 5 | May 23 | May 4 |
| Hard (28°F) | May 24 | May 8 | Apr 24 |
| 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 | Jun 18 | Jun 11 | Jun 7 | Jun 5 | Jun 3 | May 31 | May 29 | May 26 | May 21 |
| 32°F | Jun 5 | Jun 1 | May 28 | May 25 | May 23 | May 19 | May 15 | May 10 | May 4 |
| 28°F | May 24 | May 19 | May 15 | May 11 | May 8 | May 4 | May 1 | Apr 28 | Apr 24 |
| 24°F | May 11 | May 5 | May 2 | Apr 29 | Apr 26 | Apr 23 | Apr 20 | Apr 17 | Apr 12 |
| 20°F | Apr 30 | Apr 24 | Apr 20 | Apr 17 | Apr 15 | Apr 12 | Apr 9 | Apr 6 | Apr 2 |
| 16°F | Apr 20 | Apr 15 | Apr 11 | Apr 8 | Apr 6 | Apr 4 | Apr 2 | Mar 30 | Mar 25 |
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 22 | Oct 4 |
| Freeze (32°F) | Sep 18 | Oct 1 | Oct 16 |
| Hard (28°F) | Sep 29 | Oct 14 | Oct 31 |
| Severe (24°F) | Oct 10 | Oct 28 | Nov 11 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 5 | Sep 11 | Sep 16 | Sep 19 | Sep 22 | Sep 24 | Sep 27 | Sep 29 | Oct 4 |
| 32°F | Sep 18 | Sep 22 | Sep 26 | Sep 29 | Oct 1 | Oct 4 | Oct 6 | Oct 11 | Oct 16 |
| 28°F | Sep 29 | Oct 3 | Oct 6 | Oct 10 | Oct 14 | Oct 17 | Oct 20 | Oct 24 | Oct 31 |
| 24°F | Oct 10 | Oct 15 | Oct 20 | Oct 24 | Oct 28 | Oct 31 | Nov 2 | Nov 5 | Nov 11 |
| 20°F | Oct 23 | Oct 29 | Nov 1 | Nov 3 | Nov 6 | Nov 8 | Nov 13 | Nov 16 | Nov 20 |
| 16°F | Nov 1 | Nov 4 | Nov 8 | Nov 12 | Nov 14 | Nov 17 | Nov 19 | Nov 23 | Nov 28 |
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: Saxon 1Wsw, Wi, about 2.7 miles away@if(!empty($station['elevation_ft'])), at 1,165 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 Birch Hill, WI?
On average, the last spring frost (32°F) around Birch Hill, WI is about May 23. In cooler years it can run later, so for a safer bet many gardeners wait until May 4.
When is the first frost in the fall?
The first fall frost around Birch Hill, WI 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 23 on average, or May 4 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 132 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 54559 Planting calendar → Wisconsin frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026