How is a hurricane's category decided?
The familiar 1-to-5 scale measures wind speed, but it leaves out some of a storm's deadliest hazards.
When a hurricane approaches, one of the first things people want to know is its category. But the familiar scale from 1 to 5 measures only one aspect of a storm, and understanding what it does — and does not — capture is key to grasping the true danger.
The Saffir-Simpson scale rates hurricanes based solely on their maximum sustained wind speed. A Category 1 storm has winds of 74 to 95 miles per hour, while a Category 5 — the most extreme — has winds of 157 miles per hour or higher. Each step up represents a dramatic increase in potential wind damage, which rises exponentially rather than linearly.
Crucially, though, the category reflects wind alone. It says nothing about a storm's size, its forward speed, how much rain it will drop, or the height of its storm surge — the wall of ocean water pushed ashore that is historically the leading killer in hurricanes.
This is why forecasters stress that a "lower-category" storm can still be deadly. A slow-moving Category 1 hurricane can cause catastrophic freshwater flooding, as several recent storms have shown, while surge depends on factors like the shape of the coastline, not just wind speed.
Experts increasingly urge the public to focus on the specific hazards forecast for their area — surge, rainfall and wind — rather than fixating on the category number alone. The scale is a useful shorthand, but a storm is far more than its winds.