The National Weather Service has issued a dense fog advisory for the region.
The advisory is in effect for Benton, Cook, Jasper, Lake, Newton, Porter and Will counties through 8 a.m. and for LaPorte County until 10 a.m.
Unseasonably warm, moist air will keep dense fog in place through Northern Illinois and Northwest Indiana through daybreak. The fog is expected to dissipate south to north through mid morning.
Visibility in some areas is reduced to less than a quarter of a mile.
Indiana State Police reported no problems on Interstates 80, 94, 65 or the Indiana Toll Road as a result of the fog overnight or early Monday.
No school delays were issued as a result of the fog.