Last spring frost
May 16
Frost Dates for Clam Lake, WI
First fall frost
Sep 30
Growing season
136 days
Hardiness zone
4a
In an average year around Clam Lake, WI, the last spring frost (32°F) is about May 16 and the first fall frost is about Sep 30, 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 8 | May 27 | May 15 |
| Freeze (32°F) | May 27 | May 16 | May 1 |
| Hard (28°F) | May 18 | May 3 | Apr 20 |
| Severe (24°F) | May 7 | Apr 24 | Apr 9 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Jun 8 | Jun 3 | Jun 1 | May 30 | May 27 | May 25 | May 22 | May 19 | May 15 |
| 32°F | May 27 | May 24 | May 21 | May 18 | May 16 | May 13 | May 9 | May 5 | May 1 |
| 28°F | May 18 | May 13 | May 9 | May 6 | May 3 | May 1 | Apr 29 | Apr 25 | Apr 20 |
| 24°F | May 7 | May 2 | Apr 30 | Apr 27 | Apr 24 | Apr 21 | Apr 17 | Apr 14 | Apr 9 |
| 20°F | Apr 27 | Apr 23 | Apr 19 | Apr 16 | Apr 14 | Apr 11 | Apr 8 | Apr 5 | Apr 2 |
| 16°F | Apr 22 | Apr 17 | Apr 13 | Apr 10 | Apr 7 | Apr 5 | Apr 3 | Apr 1 | Mar 26 |
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 7 | Sep 20 | Oct 2 |
| Freeze (32°F) | Sep 17 | Sep 30 | Oct 12 |
| Hard (28°F) | Sep 27 | Oct 10 | Oct 24 |
| Severe (24°F) | Oct 8 | Oct 23 | Nov 6 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 7 | Sep 12 | Sep 15 | Sep 18 | Sep 20 | Sep 22 | Sep 25 | Sep 28 | Oct 2 |
| 32°F | Sep 17 | Sep 21 | Sep 24 | Sep 27 | Sep 30 | Oct 2 | Oct 4 | Oct 8 | Oct 12 |
| 28°F | Sep 27 | Oct 1 | Oct 4 | Oct 7 | Oct 10 | Oct 13 | Oct 16 | Oct 20 | Oct 24 |
| 24°F | Oct 8 | Oct 13 | Oct 17 | Oct 20 | Oct 23 | Oct 26 | Oct 30 | Nov 1 | Nov 6 |
| 20°F | Oct 19 | Oct 24 | Oct 29 | Nov 1 | Nov 2 | Nov 5 | Nov 8 | Nov 11 | Nov 16 |
| 16°F | Oct 30 | Nov 2 | Nov 5 | Nov 8 | Nov 11 | Nov 13 | Nov 16 | Nov 20 | Nov 25 |
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: Clam Lake 4W, Wi, about 4 miles away@if(!empty($station['elevation_ft'])), at 1,498 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 Clam Lake, WI?
On average, the last spring frost (32°F) around Clam Lake, WI is about May 16. 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 Clam Lake, 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 16 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 54517 Planting calendar → Wisconsin frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026