Frost dates · Illinois
Illinois frost dates, county by county.
Last spring frost and first fall frost probability data for all 102 counties in Illinois, computed from the NOAA 1991–2020 Climate Normals. Every county page surfaces the full probability table at three temperature thresholds plus crop-specific planting guidance.
Variation across Illinois
32 days separate the earliest and latest counties.
The median last spring frost in Wabash County is March 22 — 32 days earlier than Carroll County at April 23. Statewide averages aren't useful planting tools; pick your county below for the data that actually applies to your fields.
By geography
Illinois counties on the map.
Each polygon is a county. Click for full frost-date detail. Color shows last-spring-frost timing — sage = earliest, amber = latest.
MapList
Last spring frostEarliestMedianLatest
102 counties · click any county for full frost data