A Midwestern storm that may become the region’s second-most severe on record knocked out power to thousands in Illinois, Indiana and Michigan and forced the cancellation of hundreds of flights at Chicago airports.

The cyclonic system, whipping thunderstorms off its tail, was moving northeast into Canada while lashing states in the eastern and central U.S. with wind, rain and tornadoes.

The storm’s central pressure, an indication of its strength, was one of the lowest recorded in the Northern Hemisphere at about 8:30 a.m. Chicago time, said Travis Hartman, energy weather manager and meteorologist for MDA Federal Inc.’s EarthSat Energy Weather.

“It’s actually pretty impressive; we’re seeing wind, hail, rain, tornadoes — pretty much the sky is the limit,” Hartman said. “Everywhere from Chicago to the Appalachian Mountains looks to see some sort of severe weather.”

The pressure is equivalent to a Category 2 hurricane.