Decatur, IL Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Decatur, a city in Macon County, Illinois.
This Afternoon
73°F
Slight Chance T-storms
A slight chance of thunderstorms and a slight chance of rain between 1pm and 2pm, then a chance of rain and a slight chance of thunderstorms. Mostly cloudy, with a high near 73. South southeast wind 18 to 23 mph, with gusts as high as 37 mph. Chance of precipitation is 50%. New rainfall amounts less than a tenth of an inch possible.
7-day forecast for Decatur
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| This Afternoon | 73°F | Slight Chance T-storms | 18 to 23 mph SSE | 54% |
| Tonight | 55°F | Rain | 16 to 20 mph S | 84% |
| Wednesday | 60°F | Slight Chance Light Rain then Mostly Cloudy | 13 to 16 mph SW | 21% |
| Wednesday Night | 44°F | Mostly Cloudy | 12 mph SW | 1% |
| Thursday | 61°F | Mostly Sunny | 9 to 15 mph WSW | 4% |
| Thursday Night | 43°F | Mostly Cloudy then Slight Chance Light Rain | 3 to 8 mph WNW | 20% |
| Friday | 55°F | Mostly Cloudy | 7 to 12 mph NNW | 13% |
| Friday Night | 36°F | Mostly Cloudy | 2 to 10 mph NNW | 6% |
| Saturday | 53°F | Mostly Sunny | 2 to 6 mph NW | 1% |
| Saturday Night | 34°F | Partly Cloudy | 3 mph W | 2% |
| Sunday | 59°F | Sunny | 2 to 10 mph W | 9% |
| Sunday Night | 34°F | Mostly Clear | 3 to 7 mph WNW | 6% |
| Monday | 63°F | Sunny | 3 to 12 mph WSW | 3% |
| Monday Night | 39°F | Mostly Clear | 5 to 8 mph WSW | 2% |
Forecast source: National Weather Service (api.weather.gov) for Decatur (39.856, -88.934). Updated through the day.
Growing snapshot for Decatur
Last spring frost
Apr 14
First fall frost
Oct 24
Growing season
192 days
Hardiness zone
6a
More local growing data for Decatur: nearby ZIP 62523 weather · frost dates · planting calendar · Illinois frost dates
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Warrensburg
Climate data from the nearest NOAA station, Decatur Wtp, Il (1 mi from Decatur). Frost dates are 1991–2020 averages, not a forecast. Page updated Nov 3, 2026.