Understanding storm and hurricane categories: Why wind speed isn't the whole story
Tropical systems begin as tropical depressions, which are areas of low pressure with wind speeds of up to 38 miles per hour. When those winds strengthen and reach between 39 and 73 miles per hour, the system is upgraded to a tropical storm, at which point it receives a name from that year's official storm list.
Once a tropical storm's wind speed hits 74 mph or more, it becomes a hurricane and is categorized using the Saffir-Simpson Hurricane Wind Scale, which ranks hurricanes from Category 1 to Category 5 based solely on sustained wind speed.
Saffir-Simpson Scale: A breakdown of hurricane categories
- Category 1 hurricanes are considered the weakest on the scale, with wind speeds of 74 to 95 mph. These storms can produce 3 to 4 feet of storm surge, down small trees, and cause moderate damage to roofs and siding.
- Category 2 hurricanes have wind speeds between 96 and 110 mph, bringing 5 to 8 feet of storm surge. They are strong enough to uproot larger trees, damage homes more severely, and block roadways with debris and flooding.
Once a storm reaches 111 mph, it is classified as a major hurricane — a designation that includes Category 3 to Category 5 storms.
Category 3 hurricanes range from 111 to 129 mph and can produce storm surges up to 10 to 12 feet, causing significant structural damage and widespread power outages.
Category 4 hurricanes have wind speeds of 130 to 156 mph, with storm surges reaching 13 to 18 feet. These storms can make large areas uninhabitable for extended periods.
Category 5 hurricanes, the strongest classification, have winds of 157 mph or greater. With storm surge exceeding 18 feet, these catastrophic storms often leave behind widespread devastation and long-term displacement.
The Saffir-Simpson Scale doesn't tell the full story
Despite its usefulness in measuring wind intensity, the Saffir-Simpson Scale does not account for storm surge, rainfall, flooding or the size and speed of the storm. These variables can dramatically alter the impact of a storm, regardless of its category.
For example, a slow-moving Category 1 hurricane may dump more rain and cause more flooding than a fast-moving Category 3. Similarly, a large Category 2 storm could push more water inland than a small Category 4.
As a storm approaches, the NEXT Weather team goes beyond the category to provide detailed forecasts. They monitor all factors — storm size, forward speed, surge potential, and rainfall risk — to help viewers understand how any given storm may affect their specific area.
When a tropical system is on the horizon, remember: wind speed is only one piece of the puzzle.
