CHICAGO — A storm drawing comparisons to a hurricane muscled across the Midwest on Tuesday, snapping trees and power lines, delaying flights at one of nation’s busiest airports and soaking commuters who slogged to work under crumpled umbrellas.

The storm — quickly nicknamed a “chiclone” and “windpocalypse” — swept an area that stretched from the Dakotas to the eastern Great Lakes. Severe thunderstorm warnings blanketed much of the Midwest and tornado watches were issued from Arkansas to Ohio. Flights were delayed at O’Hare International Airport, a major hub for American and United airlines.

Sustained winds of 35 to 40 mph and gusts up to 60 mph were expected throughout the afternoon, the National Weather Service said.

Meteorologist Amy Seeley described the storm as one of the worst in decades based on a reading of the pressure level at its center, which was similar to a Category 3 hurricane — although the effects of the storm were not. The wind gusts were only as strong as a tropical storm; Category 3 hurricanes have winds from 111 to 130 mph.

“This is a very different type of event,” said Edward Fenelon, a National Weather Service meteorologist in Romeoville, Ill. “But that does give an indication of the magnitude of the winds. This isn’t something you see even every year.”

The winds blew off roofs at a tractor plant in Mount Pleasant, Wis., and a home in Peotone, Ill.

Sheryl Uthemann, 49, of South Milwaukee, was working first shift at the Case New Holland plant in Mount Pleasant when the storm blew through about 8 a.m. and started to lift up the roof.

“It was just a regular work day and all of a sudden that noise just came and (co-workers) said ‘Run! Run! Run!’ You didn’t have time to think,” she said. “I looked up where the noise was coming from and saw pieces of the roof sucked up. I’ve never been more scared, ever.”

Commuters in the Chicago area faced blustery, wind-driven rain as they waited for trains to take them downtown before dawn. Some huddled beneath train overpasses to stay out of the gusts, dashing to the platform at the last minute. In the city’s downtown Loop, construction workers wore heavy rain coats and held onto their hard-hats, heavy metal streets signs rattled against their posts and umbrellas provided relief only for as long as they could last.

“The wind was almost blowing horizontally. The rain was slapping me in the face,” said Anthony Kwit, a 24-year-old jewelry store worker in Chicago. “My umbrella shot off … It was pretty dangerous.”

He said the wind was so strong that his car “was starting to veer off the road.”

Another commuter described a frightening pre-dawn drive to the train station.

“It was raining really, really hard. Coming down the street I was kind of getting really nervous; even with the bright lights you couldn’t see in front of you,” said Delphine Thompson, 53, a telecom manager in Chicago.

The weather service said gusts that topped 50 miles per hour slammed into the Chicago suburb of Lombard early Tuesday.

Federal Aviation Administration spokesman Tony Molinaro said that flights were delayed early Tuesday morning at O’Hare International Airport because the airport was able to use only two runways for arrivals and one for departures. By mid-morning, the delays were down to 15 to 30 minutes, he said.

Indianapolis International Airport also reported some flight delays.

The storm also picked up speed on Twitter, where people dubbed it “Chiclone” and “Windpocalypse.”

In St. Louis, pre-dawn strong winds were blamed for a partial building collapse that sent bricks, mortar, roofing and some window air conditioning units raining down onto a sidewalk. No one was injured, and inspectors were inspecting the 1920s-era building.

In Ballwin, a St. Louis suburb, a woman escaped with minor injuries when a tree fell onto her home as she slept, covering her and her husband with dust and insulation. The family managed to get out of the house and call emergency responders.

In Milwaukee, some restaurants moved sidewalk furniture indoors as the storm approached and homeowners scrambled to batten down anything that might be swept away by the storm.

Utilities in Indiana, Illinois and the St. Louis area said more than 80,000 homes and businesses were without power.

Meanwhile, much of North Dakota was expecting its first significant snowfall of the season. The National Weather Service issued a blizzard warning, saying up to 10 inches of snow could fall in some areas into early Wednesday.

The snow is expected across North Dakota and into northern South Dakota. Forecasters said wind gusts of more than 50 mph in many areas would make travel treacherous.

Fenelon of the National Weather Service said the winds will subside Tuesday evening but could pick up again on Wednesday.

Eleven states are under a high wind warning: Illinois, Wisconsin, Indiana, Iowa, Michigan, North Dakota, South Dakota, Nebraska, Minnesota, Ohio and parts of Kentucky.

With a nod to the coming weekend, Jodi WhiteJones in Chicago said she hoped the storm wouldn’t lead to a Halloween-related disaster.

“Everyone in Chicago is used to foul weather but with this type of wind I just hope nobody gets hurt by things falling from buildings, flying pumpkins, debris,” said the 41-year-old assistant college dean at the University of Illinois at Chicago.

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Associated Press writers Tamara Starks in Chicago, David Aguilar in Detroit, Jim Suhr in St. Louis and Gretchen Ehlke in Milwaukee contributed to this story.