Decatur, IL Weather & Growing Conditions
Tonight
54°F
Light Rain
Rain before 3am, then a chance of rain showers. Cloudy. Low around 54, with temperatures rising to around 59 overnight. South wind 16 to 21 mph, with gusts as high as 26 mph. Chance of precipitation is 100%. New rainfall amounts between a half and three quarters of an inch possible.
7-day forecast
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Tonight | 54°F | Light Rain | 16 to 21 mph S | 95% |
| Wednesday | 60°F | Slight Chance Rain Showers then Mostly Cloudy | 14 to 17 mph SW | 19% |
| Wednesday Night | 43°F | Mostly Cloudy | 13 mph SW | 1% |
| Thursday | 61°F | Mostly Sunny | 12 to 16 mph WSW | 4% |
| Thursday Night | 41°F | Mostly Cloudy then Slight Chance Light Rain | 5 to 9 mph WNW | 17% |
| Friday | 55°F | Mostly Cloudy | 7 to 13 mph NNW | 14% |
| Friday Night | 35°F | Mostly Cloudy | 3 to 12 mph NNW | 6% |
| Saturday | 53°F | Mostly Sunny | 6 mph NW | 1% |
| Saturday Night | 32°F | Partly Cloudy | 5 mph W | 1% |
| Sunday | 59°F | Sunny | 3 to 12 mph W | 10% |
| Sunday Night | 33°F | Mostly Clear | 5 to 8 mph WNW | 6% |
| Monday | 63°F | Sunny | 5 to 14 mph WSW | 2% |
| Monday Night | 37°F | Mostly Clear | 6 to 9 mph WSW | 2% |
| Tuesday | 66°F | Sunny | 8 mph WNW | 1% |
Forecast source: National Weather Service (api.weather.gov). Updated through the day.
Growing snapshot for Decatur, IL
Last spring frost
Apr 16
First fall frost
Oct 22
Growing season
187 days
Hardiness zone
6a
Explore more for Decatur, IL: full frost dates · planting calendar · Illinois frost dates
Climate data from the nearest NOAA station, Decatur Ap, Il (6.9 mi). Frost dates are 1991–2020 averages, not a forecast. Page updated Nov 4, 2026.