Hurricane categories explained¶
This page explains hurricane categories so you know what the number in a forecast does and does not tell you. If you take one thing from it, take this: category measures wind only.
The Saffir-Simpson Hurricane Wind Scale¶
The Saffir-Simpson Hurricane Wind Scale rates hurricanes from 1 to 5 based on their maximum sustained wind speed. Sustained wind means the average wind over one minute, not the strongest gust. Gusts can be much higher than the sustained speed.
| Category | Sustained winds | Typical wind damage |
|---|---|---|
| 1 | 119 to 153 km/h (74 to 95 mph) | Some damage to roofs, shingles, siding, and gutters. Large tree branches snap. Shallow rooted trees may fall. Power outages that last days. |
| 2 | 154 to 177 km/h (96 to 110 mph) | Major roof and siding damage. Many trees uprooted, blocking roads. Near total power loss that can last from days to weeks. |
| 3 | 178 to 208 km/h (111 to 129 mph) | Major damage. Roof decking and gable ends removed from well built homes. Many trees snapped or uprooted. Electricity and water unavailable for days to weeks. |
| 4 | 209 to 251 km/h (130 to 156 mph) | Severe damage. Loss of most of the roof structure and some exterior walls. Most trees down. Power outages lasting weeks to months. Areas may be uninhabitable for weeks or months. |
| 5 | 252 km/h (157 mph) or higher | Catastrophic damage. A high percentage of framed homes destroyed. Fallen trees and power poles isolate neighborhoods. Areas may be uninhabitable for months. |
Categories 3, 4, and 5 are called major hurricanes. That label is about wind damage potential. It does not mean that a Category 1 or 2 is safe.
What each category looks like¶
Category 1 winds are strong enough to send loose objects flying and to peel shingles from a roof. Trees with shallow roots can come down on cars, houses, and power lines. Most people who stay in a sturdy building away from the water get through the wind fine, but power can be out for days.
Category 2 winds cause widespread damage to roofs and siding. So many trees come down that roads can stay blocked for days. Expect the power to go out almost everywhere in the path and stay out for a while.
Category 3 is where well built homes start losing parts of their roofs and where mobile homes are usually destroyed. Water and electricity are often out for weeks. This is the level at which many areas call for broad evacuations, though surge zones may evacuate for weaker storms.
Category 4 winds can take the whole roof off a house and knock down exterior walls. Nearly all trees are snapped or uprooted. Neighborhoods can be cut off, and repairs take months.
Category 5 winds destroy a large share of framed homes outright. Few structures other than reinforced concrete buildings hold up well. Recovery is measured in months or years.
Tropical depressions and tropical storms¶
Not every tropical system is a hurricane. The National Hurricane Center uses the same wind speed rule to separate the weaker stages.
| Stage | Sustained winds |
|---|---|
| Tropical depression | 62 km/h (38 mph) or less |
| Tropical storm | 63 to 118 km/h (39 to 73 mph) |
| Hurricane | 119 km/h (74 mph) or higher |
A tropical depression is an organized cluster of storms with a closed circulation but weak winds. A tropical storm has winds strong enough to get a name. Once winds reach 119 km/h (74 mph), it becomes a hurricane.
Tropical storms deserve respect. Their winds can knock out power and topple trees. More importantly, a slow moving tropical storm can drop enormous amounts of rain and cause deadly flooding far from the coast.
Category measures wind only¶
The Saffir-Simpson scale rates one hazard: wind. It says nothing about the other things a hurricane brings.
- It does not measure storm surge. Surge depends on the size of the storm, its forward speed, the angle it hits the coast, and the shape of the seafloor near shore.
- It does not measure rainfall. Rain depends mostly on how fast the storm moves and how much moisture it carries.
- It does not measure size. Two storms with the same category can have very different wind fields, and the larger one usually does more harm.
- It does not measure tornadoes, rip currents, or how long the storm lingers.
A Category 1 can kill through water
Most hurricane deaths in the United States come from water, not wind. Storm surge and inland flooding have killed people in Category 1 storms and tropical storms. If officials tell you to leave a surge zone, leave, no matter the category.
Why people get category wrong¶
Many people hear "only a Category 1" and decide to stay. That decision has cost lives. The number is easy to remember and easy to compare, so it gets more attention than it deserves.
Forecasters now issue separate warnings for storm surge and heavy rain because of this. When you check a forecast, look for the surge forecast and the rainfall forecast, not only the category. Our page on hurricane hazards walks through each one.
How the category can change before landfall¶
A storm's category is a snapshot. Hurricanes can strengthen or weaken quickly, sometimes by more than one category in a day. Rapid intensification, when a storm gains a lot of strength in a short time, has become a common concern near the coast.
The safest approach is to prepare for one category higher than the forecast says. That way a last minute change does not catch you short. Follow the latest advisory from the National Hurricane Center and the instructions of your local officials.