Every number on this site is derived from United States federal public-domain records. This page explains the sources, how figures are computed and where the data has known limits.
Sources
- NOAA/NCEI Storm Events Database — the primary source: county-tagged severe weather events from 1950 to the present, including deaths, injuries and property damage.
- NOAA SPC SVRGIS tornado tracks — mapped tornado path geometry from 1950; we intersect each path with county boundaries to distinguish tornadoes that touched down inside a county from those that crossed in.
- FEMA OpenFEMA disaster declarations — federal declarations by county since 1953.
- FEMA National Risk Index and U.S. Census ACS — risk ratings, population and housing context.
- National Weather Service API — live alerts on the warnings page, refreshed every minute.
Known limits
- Reporting practice changed over the decades: early decades are undercounted, not calmer. Hail and wind records become systematic in 1955, most other types in 1996.
- Only county-tagged events are shown on county pages; zone- and marine-tagged reports cannot be attributed to a single county.
- All event dates are UTC. Recent entries are preliminary and may be revised by NOAA.
- Damage values are as reported, not inflation-adjusted.
This site is a historical reference, never a warning service. For official alerts visit weather.gov. Data refreshes follow NOAA’s monthly publication cycle.