Storm damage seen in far north suburban Grayslake following severe weather Sunday was caused by an EF-1 category tornado, the National Weather Service said Monday.
Preliminary survey findings from Round Lake, Hainesville and Grayslake showed that winds reached approximately 90 to 100 mph during the storm, according to a tweet from the National Weather Service. The length of the tornado's path was 7.5 miles and the maximum width was measured at 300 yards.
"Damage in the Grayslake area is indeed tornadic," the weather service tweeted Monday afternoon
Officials surveyed the damage during the morning hours after the storm, which left roofs torn off buildings and knocked power out.
The storm cut a 5-mile path through Grayslake, according to Fire Chief John Christian.
Several businesses were damaged, as well as Grayslake Central High School, which had its roof partially torn off, prompting officials to close it down until further notice, according to a statement on its website.
"Storms passing through Grayslake Sunday evening have caused damage to Grayslake Central High School. The building and District offices will be closed until 10:00 am Monday, August 3rd, until emergency services has evaluated the situation," the message said. "The school and grounds are closed until further notice. Updated information will be posted on the District and school website as it becomes available."
More than 18,000 people across the Chicago area and northern and western Illinois were left without power as of Monday morning, ComEd reported.