Tornado Risk in Williamson County, IL
Williamson County's tornado history, by the numbers
23 tornado tracks have crossed Williamson County since 1957 by NOAA's count, roughly one every 3.3 years - the Moderate band on this site's scale. That is the 57th percentile nationally for tornado frequency. Within Illinois alone, Williamson County ranks 64 of 102 counties for tornado frequency.
The number that matters more than frequency
Yes. Williamson County has recorded 3 EF4 or EF5 tornados - the strength FEMA's own safe-room guidance is built around, because a standard code-built house is not expected to survive those winds without a hardened room. A county can be lower-frequency overall and still carry this history.
Shelter and safe-room economics
Illinois does not currently have a confirmed state rebate layered on top of FEMA's 75% Hazard Mitigation cost-share, so a Williamson County homeowner should expect the full national range: $2,890-$13,280, $7,645 typical.
Power after the storm, not just shelter during it
Power loss after a tornado outbreak in Illinois often reaches homes the storm itself never touched. A battery-backup unit covers the outage without the fuel and venting a generator needs.
What Williamson County's figure does not tell you
Williamson County's figure is county-wide, not address-specific. Williamson County covers about 420 square miles, so a single touch here counts the same as a single touch in a county a fraction of that size. NOAA also documents that older records undercount weaker tornadoes from before Doppler radar became standard. Williamson County has about 67,064 residents.