Midwest under threat from hurricane-force winds in severe storm system

Organizers in Wisconsin postponed the biggest air show in the U.S. as a severe storm system threatened the Midwest with potentially hurricane-force winds, tornados, hail and thunderstorms overnight.

Threat level: More than 5.9 million people could be affected by the storm system — which saw the EAA AirVenture in Oshkosh, Wisconsin, postpone events due to be held Wednesday until the following evening amid the threat of 90 mph winds.

• Storms moving through southern Wisconsin were bringing "damaging winds along the line" and the threat of tornadoes in the southeast of the state on Thursday morning, according to the NWS.
• "Thunderstorms associated with wind damage and a risk for a tornado, will be possible from the Ohio Valley, central Appalachians and Mid-Atlantic states on Thursday," the National Weather Service's Storm Prediction Center said early Thursday.
• The National Weather Service issued a level 3 out of 5 storm outlook, an an "enhanced" risk of severe weather, across the Mid-Atlantic states on Thursday, including Washington, Baltimore and Philadelphia.

The big picture: The latest in a series of heat waves that was bringing extremely hot temperatures to the Central U.S. Wednesday contributed to the severe storm system in the Midwest, per Axios' Andrew Freedman.

• Such weather patterns often lead to so-called derecho events, characterized by an organized group of severe thunderstorms that brings damaging straight-line winds across long distances, Freedman notes.

Flashback: A derecho that struck parts of Iowa and Indiana last year caused some $7.5 billion in damages.

Editor's note: This article has been updated with new details throughout.