When to Plant Squash (Summer) in Illinois
Zucchini and yellow squash are the garden's most generous producers. You'll be sharing with neighbors by midsummer.
The Short Answer
Illinois Frost Dates
Your planting dates depend on which part of Illinois you're in. Here are the frost date ranges by region:
| Region | Zones | Last Frost (Spring) | First Frost (Fall) |
|---|---|---|---|
| Northern Illinois (Chicago) | 5a, 5b | Apr 25 - May 10 | Oct 1 - Oct 15 |
| Central Illinois | 5b, 6a | Apr 15 - May 1 | Oct 5 - Oct 20 |
| Southern Illinois | 6b, 7a | Apr 1 - Apr 15 | Oct 15 - Nov 1 |
Squash (Summer) Planting Schedule for Illinois
Northern Illinois (Chicago) (Zones 5a, 5b)
Average last frost: Apr 25 - May 10 · Average first frost: Oct 1 - Oct 15
Central Illinois (Zones 5b, 6a)
Average last frost: Apr 15 - May 1 · Average first frost: Oct 5 - Oct 20
Southern Illinois (Zones 6b, 7a)
Average last frost: Apr 1 - Apr 15 · Average first frost: Oct 15 - Nov 1
Growing Squash (Summer) in Illinois
Squash (Summer) in Illinois's Climate
Your warm summers grow spectacular squash. Direct sow or transplant from mid-May. Squash vine borer emerges in late June — monitor stem bases for sawdust-like frass. Many Midwest and mid-Atlantic gardeners plant a second round in early July to replace borer-damaged early plants with clean late-season production.
Soil Considerations for Illinois
Rich prairie soils — some of the most fertile in the country. Heavy clay in many areas. Well-suited for most vegetables. Make sure soil has warmed to at least 60°F before planting squash (summer) outside.
Illinois Climate & Growing Season
Continental climate with four seasons. Hot, humid summers. Cold winters. Good growing season length in central and southern regions. 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 Illinois: Northern Illinois (Chicago) (5a, 5b) has a last frost around Apr 25 - May 10, while Southern Illinois (6b, 7a) sees frost end around Apr 1 - Apr 15. 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:
Keep squash (summer) away from:
The Bottom Line
Last reviewed: March 29, 2026