Planting windows · soil temps · frost risk · WI and MN
Planting date
calculator
Soil temperature at your location, frost odds by zone, yield loss by planting week, and the heat units four planting dates get before fall frost. Built for Wisconsin and Minnesota corn and soybeans.
Setup
108-day corn typical for south-central WI · 95–100-day for north WI
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WI / MN frost zone
Method: approximate freeze-percentile dates by zone; they run early against station records · Sources: UW-Madison SSEC (Madison median last freeze about May 5, 1940-2024); NOAA NCEI 1991-2020 climate normals and the Midwestern Regional Climate Center for your station · Reviewed by Sigurd Lindquist, Certified Crop Adviser (CCA)
Current soil temperature
Soil 6 cm (~2")
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°F · 3-day mean
Air temp now
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°F current
Soil temp is a weather-model estimate at 6 cm (~2 in), not a probe reading. For precision, check your local extension weather station.
Corn planting window: Wisconsin
GDU accumulation by planting date: central WI average
Estimated total GDU accumulation from each planting date to the zone's 50% first-fall-frost date, for four different planting dates. Earlier planting = more heat units captured before frost. Uses WI 30-year normal GDU accumulation rates.
Early planting disease risks
Soil temperature planting guide
| Soil Temp (2") | Corn Risk | Soybean Risk | Action |
|---|---|---|---|
| ≥55°F | ✓ Ideal | ✓ Ideal | Good for both crops |
| 50–54°F | ✓ Acceptable | ✓ Acceptable | Plant if forecast shows warming trend |
| 46–49°F | △ Marginal | △ Caution | Wait 2–3 days; cold soil injury risk rises |
| 40–45°F | ✗ High risk | ✗ High risk | Do not plant; imbibitional chilling likely |
| <40°F | ✗ Do not plant | ✗ Do not plant | Significant stand and seedling disease risk |
Imbibitional chilling injury occurs when dry corn seed rapidly absorbs cold water (<50°F) within the first 24–48 hours after planting. Seed cells rupture, causing irregular emergence or outright seed death. Risk is highest with a cold rain immediately after planting in soil below 50°F.
Related Tools
Common questions
When should I plant corn in Wisconsin?
The optimal corn planting window in Wisconsin is April 25 – May 10. Soil temperature at 2" depth should be at least 50°F for 3 consecutive days before planting. Yield is about 5% down by May 20 and loses roughly 1% per day from there, then roughly 1 to 1.5 points a day in early June (UMN Lamberton, Morris and Waseca trials). Northern Wisconsin should target May 1–10 to get enough GDUs before fall frost.
When should I plant soybeans in Wisconsin?
Plant soybeans as soon as the field is fit and soil is at least 50°F. Yield falls about 0.4 bu/a per day of planting delay past May 1 (UW-Madison; 0.2–0.5 bu/a/day after Apr 25). Early planting can raise SDS pressure; manage it with variety choice and seed treatment.
What soil temperature do I need to plant corn?
Corn should be planted when soil temperature at 2" depth reaches a consistent 50°F or above for at least 3 consecutive days with a warming trend. Planting into cold (below 50°F) soils risks imbibitional chilling injury, uneven emergence, and increased seedling disease pressure.
How much yield do I lose for late corn planting?
Corn yield loss for late planting in Wisconsin: about 5% down by May 20, roughly 1% per day from May 20 to June 1, then roughly 1 to 1.5 points a day in early June (UMN Lamberton, Morris and Waseca trials). A delay from May 1 to June 1 costs on the order of 35 bu/acre in a 200 bu field, and June 10 is the last practical grain planting date for southern Wisconsin. On this page’s table, April 25 yields 2% more than May 10.
What is the last frost date in Wisconsin?
At Madison the median last spring freeze is about May 5 (UW-Madison SSEC, 1940-2024 records). The zone table on this page runs earlier than that: Southern WI 50% April 22, 90% May 5; Central WI 50% May 2, 90% May 15; Northern WI 50% May 15, 90% May 28. Treat those dates as approximate and check your nearest station in the NOAA NCEI 1991-2020 climate normals before planting. Actual dates vary year to year.
Frost data: approximate freeze-percentile dates that run early (Madison median last spring freeze is about May 5, UW-Madison SSEC, 1940-2024); check your station in the NCEI 1991-2020 normals · Soil temp: Open-Meteo forecast-model soil temperature at 6 cm · Yield penalty: corn, UW-Extension & UMN Extension; soybean, UW-Madison (Conley), approximation ·
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