Heavy downpours moved through the area, along with frequent lightning strikes as the evenign went on.
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As of 8:30 p.m., O'Hare International Airport reported 459 cancelled flights and delays averaging 63 minutes, and Midway International Airport reported 7 cancelled flights and delays averaging 34 minutes.
Early afternoon conditions were very humid and hazy, with some isolated showers popping up around the Chicago area.
At 12:30 p.m. a traffic management ground stop was issued for flights arriving at O'Hare International Airport due to weather and thunderstorms, the Federal Aviation Association said.