When to Plant Watermelon in Wisconsin
The ultimate summer treat. Watermelons need heat, space, and patience — but the payoff is pure joy.
The Short Answer
Wisconsin Frost Dates
Your planting dates depend on which part of Wisconsin you're in. Here are the frost date ranges by region:
| Region | Zones | Last Frost (Spring) | First Frost (Fall) |
|---|---|---|---|
| Northern Wisconsin | 3b, 4a | May 15 - Jun 1 | Sep 10 - Sep 25 |
| Central Wisconsin | 4a, 4b | May 5 - May 20 | Sep 20 - Oct 5 |
| Southern Wisconsin | 4b, 5a, 5b | Apr 25 - May 10 | Oct 1 - Oct 15 |
Watermelon Planting Schedule for Wisconsin
Northern Wisconsin (Zones 3b, 4a)
Average last frost: May 15 - Jun 1 · Average first frost: Sep 10 - Sep 25
Central Wisconsin (Zones 4a, 4b)
Average last frost: May 5 - May 20 · Average first frost: Sep 20 - Oct 5
Southern Wisconsin (Zones 4b, 5a, 5b)
Average last frost: Apr 25 - May 10 · Average first frost: Oct 1 - Oct 15
Growing Watermelon in Wisconsin
Watermelon in Wisconsin's Climate
Watermelon pushes the limits of cold-climate gardening. Choose short-season varieties only — Sugar Baby (75 days), Blacktail Mountain (75 days, bred for northern conditions). Start indoors 3 weeks before last frost. Black plastic mulch and row cover are essential. Expect smaller fruits than southern growers — but a sun-warmed watermelon from your own cold-climate garden is incomparably satisfying.
Soil Considerations for Wisconsin
Rich agricultural soils in southern half. Sandy soils in central plain. Heavy clay in some lake regions. Generally fertile. Make sure soil has warmed to at least 70°F before planting watermelon outside.
Wisconsin Climate & Growing Season
Cold winters. Warm summers. Lake Michigan moderates eastern climate. Good growing season in south. Short season in north. Watermelon cannot tolerate any frost, so wait until all frost danger has passed before transplanting outside. Watch local forecasts carefully in spring.
Growing season length varies across Wisconsin: Northern Wisconsin (3b, 4a) has a last frost around May 15 - Jun 1, while Southern Wisconsin (4b, 5a, 5b) sees frost end around Apr 25 - May 10. This difference matters for watermelon — transplant timing shifts by several weeks across the state.
Growing Tips
Black plastic mulch warms soil faster. Check ripeness by looking for a yellow ground spot and listening for a hollow thump.
Companion Planting
Plant watermelon alongside these companions for better growth:
Keep watermelon away from:
The Bottom Line
Last reviewed: March 29, 2026