How Likely Is a Tornado in Johnson County, IL?
Johnson County's tornado history, by the numbers
Johnson County has recorded 20 tornado touches in NOAA's 76-year database, a rate of roughly one every 3.8 years - our Moderate band. Put another way: Johnson County sees more tornado activity than 50% of US counties. Within Illinois alone, Johnson County ranks 74 of 102 counties for tornado frequency.
Beyond the frequency band: violent history
9 weak and 11 significant tornadoes make up Johnson County's 20-track record - none violent. NOAA has never logged an EF4 or EF5 crossing this county.
The dollar figure Johnson County's rating leads to
Cost nationally: $2,890-$13,280, about $7,645 typical. Illinois has no state rebate program confirmed here; FEMA's underlying 75% cost-share exists nationwide, but applying through a state program is what usually makes it real, and none was found for Illinois this pass.
What a direct hit isn't required for
A direct hit is not required for Johnson County to lose power - outbreak-wide outages across Illinois regularly reach homes and businesses well outside the actual tracks. A battery bank covers that gap without a generator's fuel and venting needs.
What this number is, and is not
One caveat before relying on Johnson County's number: it is county-wide, and it covers about 344 square miles, so a single touch counts the same as one in a county a fraction of that size. Weaker pre-1990s tornadoes are also documented as undercounted in NOAA's own record. Johnson County has about 13,320 residents.