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Frost Dates in Wisconsin
First and last frost dates across Wisconsin, computed from 93 NOAA weather stations (1991–2020 climate normals). Your exact date depends on your city and microclimate — use the ZIP lookup on the main tool for a station-specific answer.
Last spring frost
May 6
statewide median · range Apr 19–May 26
First fall frost
Oct 5
statewide median · range Sep 22–Oct 29
Growing season
151 days
median · range 118–192
Stations used
93
NOAA 1991–2020 normals
Frost dates by city
Median dates from the nearest NOAA station to each city. The "cautious" date is the 10% spring value — planting after it means only a ~10% chance of a later frost.
| City | Nearest station | Last spring frost | First fall frost | Growing season | Safe transplant |
|---|---|---|---|---|---|
| Milwaukee | Milwaukee Mitchell Ap · 6 mi | Apr 19 (cautious: May 2) | Oct 29 | 192 days | May 3 |
| Madison | Uw Arboretum - Madison · 3 mi | May 1 (cautious: May 17) | Oct 9 | 161 days | May 15 |
| Green Bay | Green Bay · 4 mi | Apr 30 (cautious: May 16) | Oct 9 | 161 days | May 14 |
How frost varies across Wisconsin
Spring frost timing spans about 37 days across the state. Milwaukee Mitchell in southeastern Wisconsin typically sees its last spring frost around April 19, while Crivitz High Falls in northeastern Wisconsin doesn't clear frost until about May 26. Within any city, low spots and valleys run colder than the station average; areas near buildings and pavement run warmer.
When to plant in Wisconsin
As a rule of thumb, cool-season crops (lettuce, peas, spinach) can go in 2–4 weeks before your last spring frost; warm-season transplants (tomatoes, peppers) should wait about 2 weeks after it — around May 20 for the statewide median. Check your city's row above rather than the statewide median: a 37-day statewide spread makes the city-level date the one that matters.
These are climate normals (what's typical), not forecasts. For the current year, watch the 10-day forecast around your planting date.
How this is computed
Statewide medians are the median of the 93 NOAA stations' median frost dates — half the stations run earlier, half later. City rows use the nearest station with 30-year freeze records. Dates are 32°F freeze probabilities from NOAA NCEI 1991–2020 U.S. Climate Normals; nothing is estimated or interpolated.
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Frequently asked questions
When is the last frost date in Wisconsin?
The statewide median last spring frost is May 6, but it ranges from April 19 to May 26 depending on where in the state you are. Use your city's row in the table above, or the ZIP lookup on the main tool, for a station-specific date.
When can I plant tomatoes outside in Wisconsin?
Warm-season transplants like tomatoes should wait about two weeks after your last spring frost — around May 20 for the statewide median. Your city may differ by weeks; check the "safe transplant" column in the city table.
How long is the growing season in Wisconsin?
The median growing season across 93 NOAA stations is 151 days, ranging from 118 to 192 days by location.
Why do frost dates vary so much within Wisconsin?
Frost timing follows latitude, elevation, and local terrain. Across Wisconsin, last spring frost dates span about 37 days — from around April 19 near Milwaukee Mitchell to May 26 near Crivitz High Falls. Microclimates (low spots, valleys, urban heat) shift dates further at the garden level.
Where does this data come from?
All frost dates are computed from the NOAA National Centers for Environmental Information 1991–2020 U.S. Climate Normals freeze data (public domain), using each station's 32°F freeze probability statistics. No dates are estimated or interpolated.