Hurricane Categories Don't Tell You Anything About The Water

The Hurricane wind scale classifies storms into five wind speed categories — but storms lower on that scale can still cause life-threatening flooding.
Posted at 5:59 PM, Aug 30, 2019

Most hurricanes that strike the U.S. are not major storms: only about a third of them are category 3 or higher. But a hurricane's category doesn't convey all of its risks. 

Categories only measure wind speed. They don't account for the area a storm covers or measure rainfall or storm surge — which are deadlier than hurricane winds, on average. 

And recent history shows that a low-category storm can do as much or more water damage than a storm with stronger winds. 

Hurricane Katrina made landfall as a Category 3 storm. Sandy had Category 1 winds when it flooded New York City. Much of the flooding from Harvey came while it was a tropical storm — below Category 1 on the wind scale. 

Forecasters can't say for sure yet whether future hurricanes will move slowly like Florence or Harvey did.  But they are confident that the storms will drop more rain overall — which may increase flooding risks on the ground.