State growing guide
Illinois Planting Guide
USDA Zone 5b/6a · Last frost Apr 25 · First frost Oct 22 · 180 days
Zone-specific planting calendar, major city frost dates, top crops, and Duke's tips for growing food in Illinois.
Frost Dates by City — Illinois
Average frost dates for major Illinois cities. Use these to calculate your indoor start dates and transplant windows.
| City | USDA Zone | Last Spring Frost | First Fall Frost | Tomato Transplant Window |
|---|---|---|---|---|
| Chicago | 5b | Apr 20 | Oct 25 | ~2 wks after (Apr 20) |
| Springfield | 6a | Apr 15 | Oct 28 | ~2 wks after (Apr 15) |
| Peoria | 5b | Apr 22 | Oct 22 | ~2 wks after (Apr 22) |
| Champaign | 5b | Apr 20 | Oct 20 | ~2 wks after (Apr 20) |
| Rockford | 5a | May 5 | Oct 10 | ~2 wks after (May 5) |
Average dates based on 30-year NOAA climate normals. Individual years may vary ±2 weeks. Use the Zone Lookup Tool for ZIP-specific dates.
Duke's Top Tips for Illinois Gardeners
- Chicago gardeners: transplant tomatoes after Memorial Day (late May)
- Southern Illinois (Zone 6b) can plant 2 weeks earlier than Chicago
- Illinois summers are hot and humid — great for warm-season crops
- Plant cool-season crops (lettuce, peas, brassicas) in early April
Common Challenges in Illinois
- ⚠ Spring weather is unpredictable — surprise late frosts in May are common in northern IL
- ⚠ High summer humidity promotes fungal disease on cucumbers and squash
- ⚠ Japanese beetle damage is heavy in suburban gardens
Best Crops for Illinois
Get exact dates for your ZIP code in Illinois
City averages are a starting point. Your actual microclimate matters — enter your ZIP for precise frost dates.
Frequently Asked Questions — Illinois Gardening
What zone is Illinois?
Illinois spans Zones 5a (far north) to 6b (southern tip). Chicago is Zone 5b, Springfield is Zone 6a, Champaign-Urbana is Zone 5b.
When to plant tomatoes in Chicago?
Start tomatoes indoors in mid-March. Transplant outside after May 25 to be safe from frost. Chicago's Lake Michigan proximity can cause late cold snaps into late May.