Warm-Season Vegetable

When to Plant Squash (Summer) in Wisconsin

Zucchini and yellow squash are the garden's most generous producers. You'll be sharing with neighbors by midsummer.

The Short Answer

In Wisconsin, squash (summer) planting dates vary by region. In Northern Wisconsin, your average last frost is around May 15 - Jun 1, while Southern Wisconsin sees its last frost around Apr 25 - May 10. Since squash (summer) are frost-sensitive, start seeds indoors 3 weeks before your last frost, then transplant outside 2 weeks after frost danger has passed. Rich agricultural soils in southern half. Sandy soils in central plain. Heavy clay in some lake regions. Generally...

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

Squash (Summer) Planting Schedule for Wisconsin

Northern Wisconsin (Zones 3b, 4a)

Average last frost: May 15 - Jun 1 · Average first frost: Sep 10 - Sep 25

Start Seeds Indoors
3 wks before frost
Transplant Outside
2 wks after frost
Direct Sow
2 wks after frost

Central Wisconsin (Zones 4a, 4b)

Average last frost: May 5 - May 20 · Average first frost: Sep 20 - Oct 5

Start Seeds Indoors
3 wks before frost
Transplant Outside
2 wks after frost
Direct Sow
2 wks after frost

Southern Wisconsin (Zones 4b, 5a, 5b)

Average last frost: Apr 25 - May 10 · Average first frost: Oct 1 - Oct 15

Start Seeds Indoors
3 wks before frost
Transplant Outside
2 wks after frost
Direct Sow
2 wks after frost

Growing Squash (Summer) in Wisconsin

Squash (Summer) in Wisconsin's Climate

Summer squash (zucchini, yellow squash) is one of the most productive crops for short-season gardens — 45-60 day maturity means even 100-day seasons produce abundant harvests. Direct sow after soil reaches 60°F. Two or three plants produce more squash than most families can eat. Squash vine borer is less prevalent in cold zones, reducing the most frustrating squash pest.

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 60°F before planting squash (summer) outside.

Wisconsin Climate & Growing Season

Cold winters. Warm summers. Lake Michigan moderates eastern climate. Good growing season in south. Short season in north. Squash (Summer) 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 squash (summer) — transplant timing shifts by several weeks across the state.

Growing Tips

Harvest when fruits are 6-8 inches long for best flavor. Larger squash become seedy and tough.

Companion Planting

Plant squash (summer) alongside these companions for better growth:

Corn Beans Nasturtiums

Keep squash (summer) away from:

Potatoes

The Bottom Line

Squash (Summer) can be grown successfully across Wisconsin, but your exact planting dates depend on which region you're in. Northern Wisconsin gardeners should plan around a May 15 - Jun 1 last frost, while those in Southern Wisconsin can typically plant earlier. For exact dates based on your zip code, use our free planting date finder.

Related Guides

Squash (Summer) Growing Guide National planting guide with all states Wisconsin Planting Calendar All plants for Wisconsin Squash (Summer) in Alabama Alabama planting dates Squash (Summer) in Alaska Alaska planting dates Squash (Summer) in Arizona Arizona planting dates Squash (Summer) in Arkansas Arkansas planting dates
Note: All dates are based on NOAA 30-year Climate Normals and represent historical averages, not predictions for any specific year. Always check your local weather forecast before planting frost-sensitive crops. Learn about our data sources.

Last reviewed: March 29, 2026

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