Next 24 hours

US AQI

43Now
43
42
415 AM
41
41
418 AM
39
37
3511 AM
50
64
782 PM
82
85
885 PM
85
82
788 PM
74
69
6511 PM
60
54

Air quality outlook

Worst hour each day

Today88Moderate
Sat 1069Moderate
Sun 11500Hazardous
Mon 1296Moderate
Tue 1343Good

From our air-quality forecast models (GEOS-CF / GEFS aerosols). AQI uses the US EPA scale.

Live radar

Open full map

About Decatur weather

Decatur is in Macon County, Illinois, United States at 39.84°, -88.95°. Right now it’s 48° and clear; today’s high is 85° with a 4% chance of rain.

Illinois has a humid continental climate with distinct seasons marked by cold, snowy winters and hot, humid summers. The state's flat terrain allows weather systems to move across without obstruction, leading to rapid temperature changes. Chicago's position on Lake Michigan creates a unique lake-effect weather pattern that can moderate summer heat and intensify winter snowfall.