Hazard guide · Hurricanes

How hurricane categories work

The category number tells you about wind. It does not tell you about water, and water is what causes most hurricane deaths. Here is how to read a forecast and decide what to do.

Last reviewed October 2026

From tropical depression to hurricane

A tropical cyclone is a rotating storm system that forms over warm ocean water. Forecasters name the stages by the storm's maximum sustained wind, which is the average wind speed over one minute, measured about 33 feet above the ground.

• Tropical depression: sustained winds below 39 mph. It gets a number, not a name.
• Tropical storm: sustained winds of 39 to 73 mph. This is when a storm gets its name.
• Hurricane: sustained winds of 74 mph or more. In the western Pacific the same storm is called a typhoon.

The Atlantic hurricane season runs from June 1 to November 30. Activity usually peaks from mid-August through mid-October.

The Saffir-Simpson scale

Once a storm reaches hurricane strength, the National Hurricane Center rates it from Category 1 to Category 5 using the Saffir-Simpson Hurricane Wind Scale. Category 3 and higher are called major hurricanes.

What the category leaves out

The scale measures only wind. A Category 1 storm can still be deadly, and a few of the most destructive US hurricanes were not especially strong by wind speed at landfall. Three things the number does not capture:

• Storm surge. This is the rise of seawater pushed ashore by the storm, above the normal tide. It can reach many feet within minutes and move far inland in low-lying areas. Surge depends on the storm's size, speed and angle of approach and on the shape of the coastline, not just its category.
• Rainfall. Slow-moving storms can drop well over a foot of rain and cause flooding hundreds of miles from the coast, days after landfall. Weaker storms often move slower.
• Size. A large storm spreads damaging winds and surge over a much wider area than a compact storm of the same category.

Reading the forecast cone

The National Hurricane Center's track forecast shows a white "cone" around the predicted path. The cone shows where the center of the storm is likely to go. Historically, the center stays inside the cone about two-thirds of the time.

The cone is not a map of who will be affected. Wind, rain and surge regularly extend well outside it. If you are near the edge of the cone, or just outside it, prepare as if you are in it.

Storms can also strengthen fast. Forecasters call it rapid intensification when sustained winds increase by at least 35 mph in 24 hours. A storm forecast to be a Category 1 can arrive as a Category 3, so plan for one category higher than the forecast.

Watches and warnings

• Hurricane watch: hurricane conditions are possible in your area, usually within 48 hours. Finish your preparations and review your evacuation plan.
• Hurricane warning: hurricane conditions are expected, usually within 36 hours. Finish preparing and leave if officials tell you to.
• Storm surge warning: there is a danger of life-threatening flooding from rising water moving inland. Treat this as a reason to evacuate.

Warnings are issued early because outdoor work becomes dangerous once tropical-storm-force winds arrive, which is often many hours before the storm's center.

Deciding whether to leave

Know your evacuation zone before the season starts. Your county or state emergency management office publishes zone maps, often searchable by address. If officials order your zone to evacuate, go. Leaving early means lighter traffic and more choices for where to stay.

You may not need to go far. Moving tens of miles inland, out of the surge zone, is often enough. If you are not in an evacuation zone and live in a sturdy home, sheltering in place may be the safer choice, since the roads will be crowded. Mobile homes are not safe in hurricane winds at any category.

Where to shelter if you stay: see it in 3D

Sources: NOAA National Hurricane Center (nhc.noaa.gov); National Weather Service; Ready.gov.