National Weather Service Forecast for: Decatur IL
Issued by: National Weather Service Lincoln, IL
Updated: 11:21 pm CDT Jun 29, 2026
 
Tonight

Tonight: Mostly clear, with a low around 76. South southwest wind 8 to 10 mph, with gusts as high as 18 mph.
Mostly Clear

 Tuesday

Tuesday: Mostly sunny, with a high near 94. Heat index values as high as 106. South southwest wind 8 to 14 mph, with gusts as high as 21 mph.
Mostly Sunny

 Tuesday
Night
Tuesday Night: Clear, with a low around 75. South southwest wind 8 to 11 mph, with gusts as high as 20 mph.
Clear

 Wednesday

Wednesday: Sunny, with a high near 94. Heat index values as high as 105. South southwest wind 6 to 10 mph, with gusts as high as 17 mph.
Sunny

 Wednesday
Night
Wednesday Night: Clear, with a low around 75. South wind 7 to 10 mph, with gusts as high as 16 mph.
Clear

 Thursday

Thursday: Sunny, with a high near 93. South southwest wind 7 to 9 mph, with gusts as high as 15 mph.
Sunny

 Thursday
Night
Thursday Night: A 30 percent chance of showers and thunderstorms after 1am. Partly cloudy, with a low around 75. South southwest wind 5 to 7 mph.
Partly Cloudy
then Chance
T-storms
 Friday

Friday: A 40 percent chance of showers and thunderstorms. Mostly sunny, with a high near 92.
Chance
T-storms
 Friday
Night
Friday Night: Partly cloudy, with a low around 73.
Partly Cloudy
Lo 76 °F Hi 94 °F Lo 75 °F Hi 94 °F Lo 75 °F Hi 93 °F Lo 75 °F Hi 92 °F Lo 73 °F

Hazardous Weather Outlook
Heat Advisory
 

Tonight
 
 Mostly clear, with a low around 76. South southwest wind 8 to 10 mph, with gusts as high as 18 mph.
Tuesday
 
 Mostly sunny, with a high near 94. Heat index values as high as 106. South southwest wind 8 to 14 mph, with gusts as high as 21 mph.
Tuesday Night
 
 Clear, with a low around 75. South southwest wind 8 to 11 mph, with gusts as high as 20 mph.
Wednesday
 
 Sunny, with a high near 94. Heat index values as high as 105. South southwest wind 6 to 10 mph, with gusts as high as 17 mph.
Wednesday Night
 
 Clear, with a low around 75. South wind 7 to 10 mph, with gusts as high as 16 mph.
Thursday
 
 Sunny, with a high near 93. South southwest wind 7 to 9 mph, with gusts as high as 15 mph.
Thursday Night
 
 A 30 percent chance of showers and thunderstorms after 1am. Partly cloudy, with a low around 75. South southwest wind 5 to 7 mph.
Friday
 
 A 40 percent chance of showers and thunderstorms. Mostly sunny, with a high near 92.
Friday Night
 
 Partly cloudy, with a low around 73.
Independence Day
 
 A 30 percent chance of showers and thunderstorms after 1pm. Mostly sunny, with a high near 92.
Saturday Night
 
 A chance of showers and thunderstorms. Partly cloudy, with a low around 72.
Sunday
 
 A chance of showers and thunderstorms. Mostly sunny, with a high near 90.
Sunday Night
 
 A chance of showers and thunderstorms. Partly cloudy, with a low around 70.
Monday
 
 Mostly sunny, with a high near 86.

 

Forecast from NOAA-NWS for Decatur IL.