Decatur, IL Weather & Growing Conditions
This Afternoon
89°F
Slight Chance Rain Showers
A slight chance of rain showers after 4pm. Cloudy, with a high near 89. South southwest wind around 7 mph. Chance of precipitation is 20%. New rainfall amounts less than a tenth of an inch possible.
7-day forecast
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| This Afternoon | 89°F | Slight Chance Rain Showers | 7 mph SSW | 20% |
| Tonight | 69°F | Mostly Cloudy | 6 mph S | 12% |
| Sunday | 85°F | Partly Sunny then Chance Showers And Thunderstorms | 6 to 12 mph N | 31% |
| Sunday Night | 60°F | Chance Showers And Thunderstorms | 9 to 13 mph NE | 49% |
| Monday | 71°F | Showers And Thunderstorms Likely | 9 to 15 mph ENE | 66% |
| Monday Night | 54°F | Chance Rain Showers | 13 mph ENE | 47% |
| Tuesday | 68°F | Chance Rain Showers | 14 mph NE | 43% |
| Tuesday Night | 52°F | Mostly Cloudy | 6 to 12 mph NNE | 9% |
| Wednesday | 69°F | Partly Sunny | 10 mph NNE | 5% |
| Wednesday Night | 53°F | Partly Cloudy | 5 to 10 mph NNE | 0% |
| Thursday | 72°F | Partly Sunny | 5 to 8 mph NNE | 1% |
| Thursday Night | 55°F | Mostly Cloudy | 3 to 8 mph NNE | 8% |
| Friday | 75°F | Partly Sunny then Slight Chance Rain Showers | 5 to 8 mph NNE | 15% |
| Friday Night | 54°F | Slight Chance Rain Showers then Partly Cloudy | 3 to 8 mph NE | 15% |
Forecast source: National Weather Service (api.weather.gov). Updated through the day.
Growing snapshot for Decatur, IL
Last spring frost
Apr 14
First fall frost
Oct 24
Growing season
192 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 Wtp, Il (1.8 mi). Frost dates are 1991–2020 averages, not a forecast. Page updated Sep 19, 2026.