IL

Storm restoration across Brown County

Brown County sits in western Illinois along the Illinois River, placing it squarely in the path of the state's most frequent severe weather corridors. NWS St. Louis records document 14 tornadoes in the county from 1878 through 2009, including three F3 events and a 1938 tornado with a 115-mile damage path; the peak season runs April through June, with a historically notable late-season outbreak in December 2018 that affected neighboring counties. Hail and straight-line winds from supercells and derechos are a recurring warm-season threat, with southwestern Illinois averaging more than three damaging-hail days per year and periodic derecho tracks crossing the region, as occurred during the July 2024 event that produced 32 confirmed tornadoes statewide. The Illinois River along the county's eastern border is a chronic flood driver, with major crests documented across multiple decades and agricultural levees providing variable protection; winter brings significant ice-storm exposure, as Brown County falls within the west-southwest-to-northeast band that the Illinois State Climatologist identifies as the state's highest-frequency freezing-rain zone.