A tornado was spotted southwest of Chicago Wednesday night as a second round of storms swept through a large part of the Midwest — after a first wave cancelled more than 100 flights.
The tornado was confirmed northwest of Sheridan, Illinois, about 60 miles southwest of Chicago, at 8:26 p.m. local time (9:26 p.m. ET), the National Weather Service said.
Storm reports lodged with the weather service indicated a brief touchdown and tree damage.
Earlier Wednesday, more than 100 flights were cancelled at Chicago's main airport. Another 40 were scrubbed at Chicago Midway International Airport Wednesday, officials said.
A tornado watch issued for a swath of Iowa, Illinois and Indiana Wednesday evening — stretching from Cedar Rapids to Chicago and northwestern Indiana — until 1 a.m. Thursday local time.
Chicago was pummeled by rain earlier Wednesday, and more severe storms over central Illinois, northwest Indiana, and parts of Wisconsin and Iowa were expected Wednesday night, forecasters said.
"These storms will quickly become severe," the National Weather Service said.
As many as 50 million people were in the path of potentially dangerous weather, including Washington, D.C., and Baltimore.
A violent storm that uprooted trees in western Howard County ion Maryland Tuesday was confirmed to have been a EF-0 tornado, the weather service said. The twister had maximum winds of 80 mph. Tuesday's storms caused parts water to cascade down the stairs of a D.C. Metro station.
In addition to the cancelled flights at O'Hare International Airport, another 40 were scrubbed at Chicago Midway International Airport Wednesday, officials said.
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.
Meanwhile out West, high temperatures that fueled wildfires in Southern California cooled slightly in some areas.
A pair of fires east of Los Angeles, known together as the San Gabriel Complex, was at over 7 square miles in size and was 10 percent contained Wednesday, officials said. Residents of 534 of the 858 homes that had been evacuated in the Duarte area were allowed to return home.
In California near the Mexico border, a fire in the Potrero area covered a little more than 10 square miles and threatened 1,000 structures, the California Department of Forestry and Fire Protection said. The blaze, which began Sunday, was 15 percent contained Wednesday evening.
Large parts of southeastern California, southern Nevada and northwestern Arizona remained under excessive heat warnings Wednesday evening.