The possible hazards include damaging winds, large hail, an isolated tornado, and torrential downpours. Dew points and moisture levels are high, meaning storms could quickly drop 1–2 inches of rain, leading to a flash flooding threat in some areas.

ComEd reported more than 7,000 customers in DuPage County were without power as of around 4 p.m. Around 1,000 more were impacted across Chicago.

The Chicago area could see strong-to-severe thunderstorms Wednesday, with watches and warnings already active.

The Chicago area has felt less of an impact from the Trump administration’s National Weather Service cuts than offices in the Quad Cities and downstate Lincoln.

A clash of air masses on Wednesday will result in the threat of severe storms from Milwaukee and Chicago westward to Denver and the eastern Rockies.

In parts of Chicago, flash flood alerts rang Tuesday, warning of dangerous conditions as cars were stranded and submerged on highways and water rescues were conducted, but how much rain actually fell across the region and how fast did it all happen?

Wednesday will be another hot and humid day with highs in the lower 90s. Showers and storms are expected to move in during the afternoon and evening, some of which may become severe. The greatest risk with any strong to severe storms on Wednesday will be damaging wind gusts and heavy rain.

ABC7 took a closer look at how the tragedy led to the development of the city's Office of Emergency Management and Communications, and why it remains critical today.