National Weather Service United States Department of Commerce

Flood Return Period Calculator

Though this calculator is worded for the flood event return period it would work for any extreme weather event.

 

Enter the return period (ie..100 year flood)

Percent chance of occurrence

year flood %
Enter the number of years (ie..over the next 10 years)
There is a % chance that a year flood will occur over the next year(s)
year(s)