The National Weather Service Chicago issued a tornado warning for Cook and DuPage counties set to last through 12:30 a.m. Tuesday as heavy wind and rain pummeled the Chicago area.
Meteorologists and city officials advised residents to make a plan for shelter as the region faced severe storm and tornado watches remaining in effect for much of northern and central Illinois through 1 a.m. Tuesday.
The weather service upgraded its threat assessment to a level 4 of 5 late Monday afternoon and issued a severe thunderstorm warning for Chicago, set to last until 10:15 p.m., Monday night, according to social media alerts. The weather service began to announce tornado sightings throughout northern Illinois and suburban Chicago around 8 p.m.
A flood watch took effect at 6 p.m. Monday to last until 3 a.m. Tuesday, with flooding risks highest in urban areas that have seen substantial rainfall, according to NWS social media.
A tornado watch issued for the Chicago area and stretching as far east as South Bend, Indiana, advised of possible scattered hail the size of ping pong balls and wind gusts of up to 90 mph. Later alerts posted to weather service social media warned of tornadoes in parts of Kane and McHenry counties through 9:15 p.m, and in parts of DuPage County, near Aurora, through 9:30 p.m.
The National Weather Service also issued a severe thunderstorm warning including wind gusts of up to 70 mph and pea-size hail for much of northern Illinois, including Rockford, DeKalb, Elgin and Aurora through 9:15 p.m., per weather service social media updates. A severe thunderstorm warning of golf ball-size hail covering North Chicago, Waukegan and elsewhere in Lake County was set to be in effect through 8:30 p.m., the weather service advised.
The tornadoes prompted Midway and O’Hare International airports to issue a ground stop until at least 10:30 p.m., per the Federal Aviation Administration.
Four CTA lines — the Brown, Yellow, Pink and Green routes — reported “major delays” late Monday night due to weather-induced signal problems, a spokesperson said. Train service was expected to return to normal once the storms passed, the representative said.
Multiple Metra electric trains were also stopped mid-route due to high winds, including the Union Pacific North, Milwaukee District North, Union Pacific Northwest and BNSF lines, service alerts said.
ComEd reported 201,217 customers without power and 2,226 outages as of 10:30 p.m.
The city’s Office of Emergency Management and Communications warned late Monday afternoon of possible underpass, viaduct and street flooding and advised residents to seek shelter in the event of an emergency weather alert, move valuables out of areas prone to flooding and ensure they had multiple ways to receive weather information. The Metropolitan Water Reclamation District has also asked residents to reduce their water usage, to keep sewers and drains clear ahead of the rainfall, according to the OEMC advisory.
Climate change caused by human actions is making extreme weather, such as heat waves, flooding and severe storms, more common, scientists say.
Studies have also found climate change may be affecting tornado patterns. Victor Gensini, a professor at Northern Illinois University, told the Tribune earlier this year that climate change can affect the conditions necessary to create tornadoes.
Tornadoes need instability — warm moist air near the ground with cooler temperatures higher up — and wind shear — a change in wind speed or direction — to form. Instability is more potent in the warm seasons, and shear is usually stronger in the winter.
Tornadoes touching down in new areas; season is starting sooner and lasting longer, experts say
Gino Izzi, a senior meteorologist for the weather service, cautioned that the impact of the storms would likely vary across the Chicago area, northwest Indiana and southern Wisconsin.
“If a storm develops and sits in one spot, they could end up with 5 inches of rain and someone a few miles away could end up with very little rain,” he said.
Izzi urged residents to think about the safest place to take shelter before severe weather moves in.
“Well before a tornado warning is issued, you should have a plan in place about what you need to do,” he said.
For high-rise dwellers, the safest place would likely be an interior hallway, he said. People with basements should shelter there, or in a bathroom in the absence of a basement.
Residents should also consider whether they are in an area susceptible to flooding, Izzi added. People in flood-prone areas may want to check their basements to make sure they are clear of any belongings they want to protect.
Chicago Tribune’s Sarah Freishtat contributed.
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