Tornado Risk in Union County, SD
Union County, SD: what NOAA's tornado record says
21 tornado tracks have crossed Union County since 1954 by NOAA's count, roughly one every 3.6 years - the Moderate band on this site's scale. That is the 52nd percentile nationally for tornado frequency. Within South Dakota alone, Union County ranks 50 of 66 counties for tornado frequency.
The number that matters more than frequency
No violent (EF4-5) tornado has been recorded in Union County in NOAA's 76-year database. Of its 21 recorded tracks, 20 were weak (EF0-1) and 1 significant (EF2-3).
Shelter and safe-room economics
South Dakota does not currently have a confirmed state rebate layered on top of FEMA's 75% Hazard Mitigation cost-share, so a Union County homeowner should expect the full national range: $2,890-$13,280, $7,645 typical.
Power after the storm, not just shelter during it
The storm that misses Union County outright can still take its power out - outbreak-scale outages across South Dakota are common well beyond the tracked path. A battery-backup unit handles that without a generator's setup or fuel.
What Union County's figure does not tell you
Union County's figure is county-wide, not address-specific. Union County covers about 461 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. Union County has about 17,402 residents.