The Saffir-Simpson scale is used to measure Hurricanes.
More from web:
Saffir-Simpson Hurricane Wind Scale classifies hurricanes that exceed the intensity of tropical depressions and storms into 5 categories by the intensity of their winds.
This scale has a 1 to 5 rating based on a hurricane's sustained wind speed. Hurricanes reaching Category 3 and higher are considered major hurricanes because of their potential for significant loss of life and damage.
It estimates potential damage to the property. The hazards require people to take protective actions, including evacuating from that affected areas.
For more info: Check the video by nhc.noaa.gov explaining Saffir-Simpson Hurricane Wind Scale and Hurricane.