National Weather Service Forecast for: Decatur IL
Issued by: National Weather Service Lincoln, IL
Updated: 6:56 pm CDT Jun 18, 2026
 
Tonight

Tonight: Mostly clear, with a low around 56. Calm wind.
Mostly Clear

 Juneteenth

Juneteenth: Sunny, with a high near 78. West northwest wind 3 to 8 mph.
Sunny

 Friday
Night
Friday Night: Partly cloudy, with a low around 61. West wind around 5 mph becoming calm in the evening.
Partly Cloudy

 Saturday

Saturday: Mostly sunny, with a high near 81. West wind 3 to 6 mph.
Mostly Sunny

 Saturday
Night
Saturday Night: Partly cloudy, with a low around 63. Calm wind becoming east around 6 mph after midnight.
Partly Cloudy

 Sunday

Sunday: Showers likely, then showers and possibly a thunderstorm after 1pm. Some of the storms could produce heavy rainfall. High near 78. Southeast wind 8 to 15 mph, with gusts as high as 24 mph. Chance of precipitation is 90%. New rainfall amounts between 1 and 2 inches possible.
Showers
Likely then
Heavy Rain
 Sunday
Night
Sunday Night: Showers and possibly a thunderstorm before 1am, then a chance of showers. Low around 62. Southeast wind around 16 mph becoming north after midnight. Winds could gust as high as 24 mph. Chance of precipitation is 80%. New rainfall amounts between 1 and 2 inches possible.
Showers

 Monday

Monday: Partly sunny, with a high near 75.
Partly Sunny

 Monday
Night
Monday Night: Partly cloudy, with a low around 56.
Partly Cloudy
Lo 56 °F Hi 78 °F Lo 61 °F Hi 81 °F Lo 63 °F Hi 78 °F Lo 62 °F Hi 75 °F Lo 56 °F

 

Tonight
 
 Mostly clear, with a low around 56. Calm wind.
Juneteenth
 
 Sunny, with a high near 78. West northwest wind 3 to 8 mph.
Friday Night
 
 Partly cloudy, with a low around 61. West wind around 5 mph becoming calm in the evening.
Saturday
 
 Mostly sunny, with a high near 81. West wind 3 to 6 mph.
Saturday Night
 
 Partly cloudy, with a low around 63. Calm wind becoming east around 6 mph after midnight.
Sunday
 
 Showers likely, then showers and possibly a thunderstorm after 1pm. Some of the storms could produce heavy rainfall. High near 78. Southeast wind 8 to 15 mph, with gusts as high as 24 mph. Chance of precipitation is 90%. New rainfall amounts between 1 and 2 inches possible.
Sunday Night
 
 Showers and possibly a thunderstorm before 1am, then a chance of showers. Low around 62. Southeast wind around 16 mph becoming north after midnight. Winds could gust as high as 24 mph. Chance of precipitation is 80%. New rainfall amounts between 1 and 2 inches possible.
Monday
 
 Partly sunny, with a high near 75.
Monday Night
 
 Partly cloudy, with a low around 56.
Tuesday
 
 Mostly sunny, with a high near 77.
Tuesday Night
 
 Partly cloudy, with a low around 59.
Wednesday
 
 Mostly sunny, with a high near 78.
Wednesday Night
 
 Mostly clear, with a low around 59.
Thursday
 
 Mostly sunny, with a high near 79.

 

Forecast from NOAA-NWS for Decatur IL.