Daily Maps · September 29, 2026 · Archive
Flood risk by county: which counties average the most flood events a year
In the news: Hurricane Nolo tracking near Hawaii, flood advisory in Las Vegas Valley. 331 of the 3,211 counties with data match: Avg Flood Events / Year above 5. The states with the most: CA (27), MO (21), VA (20), NY (20). The largest by population: Los Angeles County, CA (9,936,690); Cook County, IL (5,225,367); Harris County, TX (4,726,177); Maricopa County, AZ (4,430,871). Sources: NOAA Storm Events.
How to read this map
The map sets one range on the county data: Avg Flood Events / Year from 5.0 to 100.0. A county is drawn solid navy when it falls inside every range, dotted when it misses one, and hatched when it reports no figure for one of the measures, so a hatched county is neither a match nor a miss. Recounted today from the county database, 331 of the 3,213 counties with a figure for every range fall inside all of them, and California has the most with 27. The count in the title is the count on the day the map ran; the two can differ when a source is refreshed.
The figures are the same ones behind every county page on this site: Census population and household income, Zillow home values, HUD fair market rents, County Health Rankings measures of crime and health, NOAA temperatures and USDA amenity scores, each stored with its publication year and listed below for this map. "Play with this map" opens the live county map with these ranges already set, so you can move a handle and watch the count change; "Make your own" starts from a blank map.
Sources
- NOAA Storm Events
Solid navy marks counties inside every range on this map, dotted counties miss one or all of them, and hatched counties have no figure for that measure. On a heatmap, darker means higher and faded counties fall outside the range.