Illinois Frost Dates & Growing Zones by City
Chicago is our only Illinois city with frost dates so far: typical (50%) last spring frost Apr 10, typical frost-free season 208 days.
On the 2023 USDA hardiness map, these cities fall in zones 6a and 6b.
Each city's dates come from the nearest NOAA station that passes our quality rules. The methodology explains how we pick it.
| City | Last frost (50%) | First frost (50%) | Season (days, 50%) | Zone 2023 | Confidence | Planting calendar |
|---|---|---|---|---|---|---|
| Chicago frost dates | Apr 10 | Nov 5 | 208 | 6a–6b | Medium | Chicago planting calendar |
Station match, data and rules: methodology. Long-term odds, not a forecast.