Decatur, IL Weather & Growing Conditions
This Afternoon
86°F
Chance Showers And Thunderstorms
A chance of showers and thunderstorms before 5pm. Mostly sunny. High near 86, with temperatures falling to around 80 in the afternoon. East northeast wind around 10 mph. Chance of precipitation is 30%.
7-day forecast
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| This Afternoon | 86°F | Chance Showers And Thunderstorms | 10 mph ENE | 28% |
| Tonight | 70°F | Partly Cloudy | 10 mph ESE | 4% |
| Saturday | 90°F | Slight Chance Showers And Thunderstorms | 9 mph SSW | 20% |
| Saturday Night | 69°F | Mostly Cloudy then Slight Chance Showers And Thunderstorms | 8 mph SSW | 23% |
| Sunday | 85°F | Chance Showers And Thunderstorms | 5 to 14 mph NNW | 47% |
| Sunday Night | 60°F | Chance Showers And Thunderstorms | 15 mph NE | 67% |
| Monday | 71°F | Showers And Thunderstorms Likely | 17 mph NE | 68% |
| Monday Night | 54°F | Showers And Thunderstorms Likely | 14 to 17 mph NE | 62% |
| Tuesday | 68°F | Chance Rain Showers | 17 mph NE | 35% |
| Tuesday Night | 52°F | Mostly Cloudy | 8 to 16 mph NNE | 8% |
| Wednesday | 70°F | Partly Sunny | 13 mph NNE | 2% |
| Wednesday Night | 53°F | Partly Cloudy | 5 to 12 mph NNE | 2% |
| Thursday | 72°F | Mostly Sunny | 6 to 10 mph NNE | 3% |
| Thursday Night | 54°F | Partly Cloudy | 5 to 10 mph NNE | 5% |
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 Sep 18, 2026.