The strongest was a long track one from Franklin Grove to north of Rochell through Fairdale and into Boone County. That has been given a rating of an EF-4 with maximum winds of 180-200 mph. The tornado caused two fatalities and 22 injuries.
Ed Fenelon is a meteorologist with the National Weather Service’s office in Chicago. He says a tornado of that magnitude is rare.
"It's actually been 25 years since we've had an EF-4 in our area of responsibility, which is the 18 counties in northern Illinois and the five counties in northwest Indiana. This is the first EF-4 tornado that we've had in Illinois since the Washington, Illinois tornado back on November 17, 2013.”
He says meteorologists drew from a catalog of damage from past storms to determine the magnitude of this event.