UPDATED Monday afternoon: The tornado that flattened Fairdale in DeKalb County last Thursday was the most severe among nine tornadoes across Illinois during the late afternoon and evening, The National Weather Service has reported. It was rated as an EF-4 with maximum winds of 180 to 200 miles per hour.
Five of those storms were in north central Illinois in the NWS Chicago County Warning Area (CWA), two in northwest Illinois in the NWS Quad Cities CWA, and two in central Illinois in the NWS Lincoln CWA.
The strongest tornado originated near Franklin Grove in Lee County and raced to north of Rochelle in Ogle County, then on through Fairdale before moving into Boone County. This tornado caused two fatalities and 22 injuries.
A tornado of this magnitude is quite rare. This was the strongest tornado for both Ogle and DeKalb Counties since 1950.
It was the first EF-4 tornado in Illinois since two EF-4 tornadoes occurred on Nov. 17, 2013, including one that struck the community of Washington, and the 33rd EF-4 or stronger tornado in Illinois on record since 1950.
It was the strongest tornado in the Chicago County Warning Area since an EF5 tornado struck Plainfield on Aug. 28, 1990.
While most of the storm surveying has been completed, there is still coordination being done with Emergency Management regarding storm damage in Boone and McHenry Counties.
The atmosphere was ripe for severe weather due to highly anomalous moisture and instability for early April across the region. A strong low-pressure system advanced into this favorable air mass, helping to trigger these potent storms.
The DeKalb County Sheriff's Department has posted an aerial video showing the extent of the damage in Fairdale.
