Two EF-1 tornadoes, one near Antioch and another near Marengo, touched down during a derecho that caused widespread damage Monday afternoon, the National Weather Service confirmed.
The National Weather Service (NWS) issued a tornado warning around 3:50 p.m. Monday for Lake and McHenry counties as the derecho swept across the Midwest.
The NWS said Tuesday evening that there were at least seven confirmed tornadoes across the Chicago area, which caused trees, debris and power lines to fall on cars, houses and roads.
Weather officials said that an EF-1 tornado, with peak winds of 95 mph, touched down around 3:05 p.m. near Interstate 90 south of Marengo and traveled 5.7 miles northeast towards Union.
It caused tree damage and heavily damaged a single-family home near Maple Street before continuing northeast and lifting near Coral and Dunham Roads.
Weather officials also confirmed a second tornado, with peak winds of 90 mph, that touched down around 3:41 p.m. near Route 173 east of Wilmot Road in unincorporated Antioch and traveled northeast for 3.75 miles into Camp Lake, Wisconsin.
Tree damage and some instances of significant structural damage was reported.
“A well-organized and long-lived complex of storms produced widespread severe wind damage across Iowa, northern Illinois, and northern Indiana during the day,” the NWS said in a statement.
“Much of this severe wind was significant (75+ mph winds) resulting in many downed trees, several topped over semi-trucks, and many communities had at least some minor structural damage,” the statement added.
A derecho produces a swath of particularly damaging thunderstorm winds over an area at least 400 miles long and 60 miles wide.
Wind speeds in a derecho can exceed 100 mph which is equivalent to that of an EF-1 tornado but over a vastly larger area than a tornado would impact.
Tornadoes can also be embedded within derechos and produce concentrated areas of even more intense damage, the NWS said.
Lake County Sheriff Spokesman Sgt. Christopher Covelli said that deputies responded to about 100 weather-related calls for service during the storm.
The majority were for trees blocking roadways, live power lines down and trees which fell causing property damage.
In one incident a tree caused structural damage to a home and another that destroyed a vehicle.
A tree fell into a home in unincorporated Lake Villa, causing the homeowner to sustain a minor injury, Covelli said.
“The majority of the calls took place in the northern and western portions of the county,” Covelli said, adding that approximately 30 calls were for live power lines down and another 30 calls for trees blocking the roadway.
McHenry County Sheriff’s Deputy Sandra Rogers said Monday evening that deputies were responding to calls of trees and power lines down in the road throughout McHenry County.
According to ComEd, 2,696 customers in McHenry County and 4,412 customers in Lake County remained without power as of 8 p.m. Tuesday.
“ComEd has more than 800 employees working around the clock to restore energy to affected customers as quickly and safely as possible. Additionally, more than 1,100 mutual assistance workers are coming in from out of state to assist in restoration efforts,” ComEd said in a statement.
“This storm caused significant damage across the service territory, including downed poles, broken lines and tree-related damage. ComEd expects that it will take multiple days to restore service to all of the customers affected by the storm,” the statement added.