There are two major scales used to interpret hurricane and tornado intensity—and thus potential damage. The Saffir-Simpson Hurricane Damage-Potential Scale is a hurricane force scale using the numbers 1 through 5 to rate a hurricane’s intensity. The scale was developed by engineer Herbert Saffir (1917–2007) and pioneer hurricane expert Robert Simpson (1912-) in 1971. A number on the scale is assigned to a hurricane based on its peak wind speed; it is also used to give an estimate of the potential property damage and flooding expected along the coast from a hurricane landfall.

The Fujita-Pearson Tornado Intensity Scale (or “F-Scale”) is used to measure tornado wind speeds. It was developed in 1971 and named after Tetsuya Theodore Fujita (1920–1998) of the University of Chicago and Allan Pearson, who was then head of the National Severe Storms Forecast Center in Kansas City. It was Fujita who came up with a system to rank tornadoes according to how much damage they cause. He developed his categories by connecting the twelve forces of the Beaufort wind scale (knots based on what the sea surface looks like—from smooth to waves over 45 feet) with the speed of sound (Mach 1). Then, for each category he estimated how strong the wind must be to cause certain observed damages. Fujita’s scale was later combined with Pearson’s scale, which measures the length and width of a tornado’s path, or its contact with the ground.