Last spring frost
May 7
Frost Dates for Green Bay, WI
First fall frost
Oct 9
Growing season
154 days
Hardiness zone
5b
In an average year around Green Bay, WI, the last spring frost (32°F) is about May 7 and the first fall frost is about Oct 9, giving roughly a 154-day growing season. To be safe most years, wait until Apr 24 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) | May 31 | May 19 | May 4 |
| Freeze (32°F) | May 22 | May 7 | Apr 24 |
| Hard (28°F) | May 12 | Apr 27 | Apr 10 |
| Severe (24°F) | Apr 27 | Apr 12 | Mar 30 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 31 | May 27 | May 24 | May 21 | May 19 | May 16 | May 13 | May 8 | May 4 |
| 32°F | May 22 | May 16 | May 13 | May 10 | May 7 | May 4 | May 2 | Apr 29 | Apr 24 |
| 28°F | May 12 | May 6 | May 2 | Apr 30 | Apr 27 | Apr 23 | Apr 20 | Apr 16 | Apr 10 |
| 24°F | Apr 27 | Apr 22 | Apr 19 | Apr 15 | Apr 12 | Apr 9 | Apr 6 | Apr 3 | Mar 30 |
| 20°F | Apr 18 | Apr 12 | Apr 8 | Apr 5 | Apr 3 | Apr 1 | Mar 29 | Mar 25 | Mar 18 |
| 16°F | Apr 8 | Apr 3 | Apr 1 | Mar 30 | Mar 27 | Mar 23 | Mar 19 | Mar 16 | Mar 12 |
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 15 | Sep 28 | Oct 12 |
| Freeze (32°F) | Sep 23 | Oct 9 | Oct 25 |
| Hard (28°F) | Oct 5 | Oct 25 | Nov 7 |
| Severe (24°F) | Oct 24 | Nov 6 | Nov 19 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 15 | Sep 19 | Sep 22 | Sep 25 | Sep 28 | Sep 30 | Oct 3 | Oct 7 | Oct 12 |
| 32°F | Sep 23 | Sep 28 | Oct 2 | Oct 6 | Oct 9 | Oct 12 | Oct 16 | Oct 20 | Oct 25 |
| 28°F | Oct 5 | Oct 11 | Oct 17 | Oct 22 | Oct 25 | Oct 28 | Oct 31 | Nov 3 | Nov 7 |
| 24°F | Oct 24 | Oct 30 | Nov 1 | Nov 3 | Nov 6 | Nov 8 | Nov 11 | Nov 14 | Nov 19 |
| 20°F | Nov 3 | Nov 6 | Nov 10 | Nov 12 | Nov 15 | Nov 17 | Nov 20 | Nov 22 | Nov 26 |
| 16°F | Nov 8 | Nov 13 | Nov 17 | Nov 19 | Nov 22 | Nov 24 | Nov 26 | Nov 30 | Dec 4 |
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: Green Bay Botanical, Wi, about 6.3 miles away@if(!empty($station['elevation_ft'])), at 694 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 Green Bay, WI?
On average, the last spring frost (32°F) around Green Bay, WI is about May 7. In cooler years it can run later, so for a safer bet many gardeners wait until Apr 24.
When is the first frost in the fall?
The first fall frost around Green Bay, WI typically arrives about Oct 9. 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 7 on average, or Apr 24 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 154 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 54302 Planting calendar → Wisconsin frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026