Note: As of 10:07 p.m. Monday night, the severe thunderstorm watch had moved out of the Chicago area.
Following a morning of severe thunderstorm warnings that led to grounded flights at Chicago's O'Hare International Airport, severe weather loomed over the afternoon forecast with chances for hail, heavy downpours, gusty damaging winds and the possibility of tornadoes.
A severe thunderstorm watch has been issued for most of the Chicago area Monday evening, covering a swath from northwestern Illinois all the way into northwest Indiana.
According to the National Weather Service, the watch will be in effect until midnight for McHenry, DeKalb, Kane, LaSalle, Kendall, Grundy, Will and Kankakee counties in Illinois. Newton and Jasper counties in Indiana are also impacted by the watch.
LIVE RADAR: Track showers, storms as severe weather threatens Chicago area
Already severe storms have fired up in parts of western Illinois, with large hail and gusty winds possible.
According to the watch, wind gusts up to 65 miles per hour are possible with some storms, along with ping pong ball-size hail and a non-zero tornado risk.
Local
Storm timing was expected to begin in the late afternoon Monday, the NBC 5 Meteorologist Alicia Roman said, with storm chances lasting into the late evening.
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According to the NWS, the entire Chicago area at that time will be under a "slight" risk of severe weather, which ranks as level two of five on the Storm Prediction Center's severe weather scale.
During the storm window, "all weather hazards will be at play," Roman said, with chances for heavy downpours, gusty, damaging winds up to 60 miles per hour, quarter-sized hail and localized flash flooding.
Additionally, the potential for a tornado can't be ruled out, Roman said.
"It's a low threat, but it's not zero this afternoon and evening," Roman said, of the chance for tornadoes.
Storms and heavy downpours could last overnight and linger into Tuesday morning, Roman said, especially in counties to the north.
"Thunderstorms may occur in far northern Illinois early Tuesday morning and in Northwest Indiana Tuesday afternoon," an alert from the NWS said. "Heavy rainfall would accompany any storms that develop which could result in localized flooding."
According to the NWS, Tuesday will also see dangerous swimming conditions at Lake Michigan beaches in Illinois and Indiana, with a high swim risk and large waves.
Temperatures Monday will remain hot and humid, Roman said, highs in the mid-to-upper 80s, but even higher dew points.
"High temperatures in the upper 80s to around 90s, combined with dew points in the mid 70s will produce heat index values of 100 to 105 degrees this afternoon," the NWS said. "Take extra precautions if you work or spend time outside."
By Tuesday, temperatures were expected to dip into the 70s, Roman said.
