Illinois Planting Guide & Growing Season
Illinois is in USDA hardiness zone 5a-7a with a growing season of 175 days. The average last spring frost is Apr 20 and the average first fall frost is Oct 10. Climate data based on Springfield.
Growing Conditions in Illinois
How Illinois Compares
Compare Illinois's growing conditions with states that have similar climates.
| State | USDA Zone | Last Frost | First Frost | Season (days) |
|---|---|---|---|---|
| Illinois (IL) | 5a-7a | Apr 20 | Oct 10 | 175 |
| Alabama (AL) | 7a-8b | Mar 15 | Nov 5 | 235 |
| Alaska (AK) | 1a-7b | May 30 | Sep 5 | 100 |
| Arizona (AZ) | 4b-10b | Mar 1 | Nov 15 | 260 |
| Arkansas (AR) | 6b-8a | Apr 1 | Oct 25 | 210 |
| California (CA) | 4b-11a | Feb 15 | Nov 30 | 290 |
Frequently Asked Questions About Gardening in Illinois
When should I start seeds indoors in Illinois?
In Illinois, the average last frost date is Apr 20. Start most seeds indoors 6-8 weeks before this date. The USDA hardiness zone for Illinois is 5a-7a, with a growing season of approximately 175 days.
What USDA hardiness zone is Illinois?
Illinois falls in USDA hardiness zones 5a-7a. This affects which perennial plants will survive winter and influences optimal planting times.
When is the first frost in Illinois?
The average first frost date in Illinois is Oct 10. Plan to harvest cold-sensitive crops before this date or protect them with row covers.
How long is the growing season in Illinois?
Illinois has an average growing season of 175 days, from the last frost (Apr 20) to first frost (Oct 10). This moderate season works well for most common vegetables.
Plan Your Garden
Use our seed starting calculator to get personalized planting dates, or browse all states.