EF1 tornado in Knox County, Illinois

A tornado touched down along Knox Road 1525 East about 1.5 miles northeast of Altona at 8:41 PM CDT. It destroyed a hog farm building and tossed it into a nearby outbuilding upon touchdown, then tracked northward into the National Weather Service Quad Cities County Warning Area in Henry County just east of the intersection of North Knox Road and East 1470th Street at 8:43 PM CDT.

A warm front lifted northward through central Illinois during the afternoon of April 20th...allowing temperatures to climb well into the 70s. As a cold front approached from the west, scattered strong to severe thunderstorms developed in the Illinois River Valley by early evening. A few of the cells began rotating, especially as they approached the warm front along and north of the I-74 corridor. Three tornadoes touched down...including 2 EF-1 tornadoes in Knox County and another EF-1 in Tazewell County. Other cells produced scattered wind damage mainly west of I-55, with an isolated damaging wind gust occurring further southeast in Clay County later in the evening as the storms advanced eastward to the Indiana border.