Millions of Americans across the Midwest were facing damaging winds, large hail, flooding and a possible tornado outbreak Wednesday.
Heavy rain pummeled Chicago early before moving into Indiana Wednesday afternoon, and storms were expected to develop again Wednesday evening in Iowa and Wisconsin, moving into Illinois and Indiana with possible tornadoes.
Accompanying the storms will be winds with gusts of up to 85 mph. The line of storms will drift over the Midwest and reach the mid-Atlantic early Thursday morning, and could meet the criteria of a phenomenon called a derecho — a widespread windstorm with over 250 miles in wind damage and regular gusts over 58 mph.
By Thursday afternoon, more storms could hit the mid-Atlantic, although they wouldn't be severe as Wednesday's and carried a lower tornado risk.
In addition to Chicago Wednesday, Indianapolis, Cincinnati, and Columbus were all under the threat area for severe thunderstorms through the day, according to forecasters.
"This area is densely populated which increases the odds of significant damage if tornadoes do form," NBC News meteorologist Bill Karins said. He added there was a "mini-tornado outbreak possible this afternoon [or] evening."
In total, about 96 million people could see stormy weather Wednesday, stretching from southern Minnesota to the East Coast.
There were two rounds of thunderstorms expected. The first was early in the day, when rain pounded the Iowa, Illinois and Wisconsin borders, prompting a patchwork of flash flood watches and warnings from Lake Michigan into South Dakota. Severe thunderstorm watches were posted in parts of Illinois and Iowa, and winds gusts of up to 66 mph were recorded in Muscatine, Iowa.
Twisters were most likely to touch down in northern Illinois but were also possible in south Michigan, northern Indiana.
The "Rockford [Illinois] to Chicago area will need to be watched closely between 4 p.m. and 8 p.m. central time [5 p.m. to 9 p.m. ET]," Karins said.
The second line of storms forecast was a single squall line expected to push east across Indiana, Ohio and Michigan by the evening, according to The Weather Channel.
The forecaster added that "we can't rule out" this squall line surviving until the mid-Atlantic states on Thursday, causing wind gusts and severe weather in Washington, D.C., and Philadelphia.
It would be the second time in three days that the mid-Atlantic has been targeted by severe weather, after heavy rain, winds of up to 80 mph and golf-ball-sized hail battered the region Tuesday.
At least 35,000 homes and businesses lost power in New Jersey following the storm and 127 flights were canceled at Baltimore-Washington International Airport, according to FlightAware.
The same day an 80 mph tornado with a preliminary EF0 rating (65-85 mph winds) touched down for more than 12 miles in Howard County, Maryland, causing damage to a house, the National Weather Service said.
There was also severe weather in the High Plains on Tuesday, and three other tornadoes were reported in North Dakota, including one that tore the roof and garage away from a home, the NWS said.
Meanwhile, excessive heat enshrouded the Midwest, with temperatures nearing 100 degrees in parts of Kansas and Oklahoma Wednesday.