A parade of severe weather was marching east on Wednesday, hours after parts of the Upper Midwest were hit with strong thunderstorms, damaging winds and numerous reports of tornadoes, leaving thousands without power.

Here’s what to know about the weather:

• Between Tuesday afternoon and Wednesday morning, tornado warnings continued to be issued across the Midwest as the line of storms rolled east.

• The storms are likely to fade in intensity through the day Wednesday.

Warnings in Ohio early Wednesday morning after dramatic weather in Chicago on Tuesday

An early picture of the damage inflicted by the storms began to emerge as officials worked to assess damage and confirm tornadoes in several communities west of Chicago on Tuesday night.

As the threat of severe weather moved east on Wednesday morning, more than 11 million people across Ohio and Kentucky were under a tornado watch Wednesday morning. The Weather Service office in Wilmington, Ohio, issued a brief tornado warning for several counties in west central Ohio, advising that debris may fly in strong winds and that mobile homes could be damaged or destroyed. Tornado watches were also issued for Indiana until 6 a.m.

Overnight, parts of Michigan appeared to be among the hardest hit, including Grand Blanc, less than 10 miles southeast of Flint. The Genesee County Sheriff’s Office said on Facebook that a tornado had struck the area around 1:20 a.m. A spokesman from the Grand Blanc Township Fire Department said that it was receiving “lots of reports of damage,” and the Genesee County Police, Fire and E.M.S. website showed reports of downed power lines and a natural gas odor in the city.

As of 6 a.m., nearly 18,000 customers in Michigan and nearly 17,000 in Ohio were without power, according to PowerOutage.us, which aggregates data from utilities across the country.

On Tuesday evening, officials at O’Hare International Airport in Chicago briefly grounded all departing flights and suspend its rail service while asking people in the airport to “exercise caution.” The NBC News affiliate in Chicago shared video of hundreds of passengers packing into the airport for shelter.

The National Weather Service confirmed there were reports of at least one tornado touchdown in Henry County in western Illinois. At least five other tornado sightings were reported by the Weather Service, including three near the city of DeKalb, roughly 60 miles west of the Chicago.

Looking ahead on Wednesday

The ongoing storms will continue to march east Wednesday but are likely to lose their intensity. As the colder air moves east it will create a line of showers and thunderstorms that stretches from the South to the Northeast. There is a possibility that storms from Tennessee to New York could see some isolated strong wind gusts from some of the more intense storms.

Behind the line of storms temperatures will plummet and the potential for moderate to heavy snow will develop over the Great Lakes into the Northeast.

Yan Zhuang contributed reporting.