what is the average annual rainfall in illinois
The average annual rainfall (total precipitation) in Illinois is roughly 38 to 40 inches per year statewide, with a clear north–south gradient.
Quick Scoop
- Northern Illinois averages just over 35 inches of precipitation per year.
- Central Illinois typically sees around 37–41 inches annually.
- Southern Illinois is wetter, with many locations close to or above 45–49 inches per year.
- In simple terms: if you imagine a “typical” spot in Illinois, planning on about 3 to 3.5 feet of precipitation per year is a good rule of thumb.
Regional snapshot (examples)
| Region / City | Average annual precipitation |
|---|---|
| Northeast Illinois (Chicago O’Hare) | About 38 inches per year | [5]
| Central Illinois (Springfield) | About 38 inches per year | [5]
| Southern Illinois (Carbondale) | About 49 inches per year | [5]
So while “average annual rainfall in Illinois” is often quoted around the upper 30s in inches, where you are in the state can shift that total by more than 10 inches a year.
TL;DR: Illinois averages around 38–40 inches of precipitation a year overall, drier in the north and noticeably wetter in the south.
Information gathered from public forums or data available on the internet and portrayed here.