Decatur, IL Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Decatur, a city in Macon County, Illinois.
This Afternoon
87°F
Mostly Sunny
Mostly sunny. High near 87, with temperatures falling to around 81 in the afternoon. East northeast wind around 9 mph.
7-day forecast for Decatur
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| This Afternoon | 87°F | Mostly Sunny | 9 mph ENE | 8% |
| Tonight | 71°F | Partly Cloudy | 9 mph ESE | 5% |
| Saturday | 92°F | Slight Chance Showers And Thunderstorms | 9 mph SSW | 19% |
| Saturday Night | 70°F | Mostly Cloudy then Slight Chance Showers And Thunderstorms | 8 mph SSW | 23% |
| Sunday | 86°F | Chance Showers And Thunderstorms | 3 to 12 mph NNW | 47% |
| Sunday Night | 61°F | Chance Showers And Thunderstorms | 14 mph NE | 67% |
| Monday | 72°F | Showers And Thunderstorms Likely | 15 mph NE | 67% |
| Monday Night | 55°F | Showers And Thunderstorms Likely | 15 mph NE | 64% |
| Tuesday | 69°F | Chance Rain Showers | 15 mph NE | 35% |
| Tuesday Night | 53°F | Mostly Cloudy | 7 to 13 mph NNE | 7% |
| Wednesday | 72°F | Partly Sunny | 12 mph NNE | 2% |
| Wednesday Night | 54°F | Partly Cloudy | 5 to 10 mph NNE | 2% |
| Thursday | 73°F | Mostly Sunny | 5 to 10 mph NNE | 3% |
| Thursday Night | 55°F | Partly Cloudy | 3 to 9 mph NNE | 5% |
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
Nearby towns & communities
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Boody
Dalton City
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Forsyth
Harristown
Long Creek
Macon
Maroa
Mount Zion
Niantic
Oreana
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 Sep 19, 2026.