A weather advisory was issued Saturday evening for northern Lake County until 9 p.m., according to the National Weather Service.
At 7:56 p.m., a strong thunderstorm was tracked moving east at 20 mph along a line stretching from Hammond to Homewood, Illinois, the NWS said.
Nickle-sized hail, wind gusts moving at 50 mph and heavy rain was predicted.
Impacted areas in Northwest Indiana include Hammond, Gary, Portage, Merrillville, East Chicago, Schererville, Hobart, Highland, Munster, Griffith and Lake Station, the NWS said.
The Midwest Collegiate League All-Star game at Whiting's Oil City Stadium had a lengthy lightning delay.
Areas of Interstate 80, Interstate 90, Interstate 94 and Interstate 65 will also be impacted, and drivers should avoid travel or travel with great caution.
The heavy rains could lead to localized flooding, and the NWS warned drivers to not travel through flooded roadways.
In Hammond, 614 people reported power outages, 68 were without power in Dyer and 40 were without power in Munster, according to the NIPSCO website.