Tropical Depression vs Tropical Storm vs Hurricane: Wind Thresholds
A tropical depression, a tropical storm and a hurricane are the same kind of system, a tropical cyclone, at different strengths. The National Hurricane Center (NHC) separates them by maximum sustained wind: a tropical depression has 38 mph (62 km/h) or less, a tropical storm has 39–73 mph (63–118 km/h), and a hurricane has 74 mph (119 km/h) or more. NOAA says the same kind of storm is called a typhoon in the Northwest Pacific and a tropical cyclone in the South Pacific and Indian Ocean.
What wind speeds separate a depression, a storm and a hurricane?
NHC measures intensity with the U.S. 1-minute average sustained surface wind. The thresholds in its glossary are set in knots, with mph and km/h equivalents.
| Stage | Sustained wind (mph) | Knots | km/h | Label |
|---|---|---|---|---|
| Tropical depression | 38 or less | 33 or less | 62 or less | A number, such as Tropical Depression Nine |
| Tropical storm | 39–73 | 34–63 | 63–118 | The next name on the season’s list |
| Hurricane | 74 or more | 64 or more | 119 or more | Keeps its name, rated Category 1–5 |
| Major hurricane | 111 or more | 96 or more | 178 or more | Category 3, 4 or 5 |
Sources: the NHC glossary and the Saffir-Simpson Hurricane Wind Scale. Our guide to hurricane categories lists all five categories with NHC’s damage descriptions.
NHC’s public advisory states whether a system is a depression, a storm or a hurricane, with its winds, position and motion. Our live page of active NHC storms and other basins shows the official advisory data and GDACS alerts for typhoons and cyclones in one place. For alerts where you live, see active NWS alerts by state.
What exactly is a tropical cyclone?
NHC defines a tropical cyclone as a warm-core, non-frontal low-pressure system that forms over tropical or subtropical waters. It has organized deep convection (thunderstorms) and a closed surface wind circulation around a well-defined center. Once formed, it runs on heat drawn from warm ocean water. Extratropical cyclones, by contrast, get their energy from temperature contrasts between air masses.
What comes before a tropical depression?
Before a system becomes a depression, NHC may track it in its Tropical Weather Outlook, which gives formation chances for the next 2 and 7 days. NHC’s glossary defines the earlier stages this way:
- Tropical wave: a trough or bend in the trade-wind easterlies.
- Tropical disturbance: a moving system of apparently organized thunderstorms, generally 100 to 300 nautical miles across, that keeps its identity for 24 hours or more.
- Potential tropical cyclone: a disturbance that is not yet a tropical cyclone but threatens tropical storm or hurricane conditions on land within 72 hours.
Potential tropical cyclones and depressions get numbers from one shared sequence for each season. The National Weather Service explains that if Potential Tropical Cyclone Four becomes a depression, it is called Tropical Depression Four. Since 2025, NHC can begin advisories on a potential tropical cyclone up to 72 hours before storm surge or tropical-storm-force winds are expected on land.
When does a storm get a name?
A system gets a name when it reaches tropical storm strength, 39 mph (63 km/h). Depressions keep only their numbers. Subtropical storms take names from the same list: in October 2026, NHC named Subtropical Storm Josephine, the tenth named storm of the Atlantic season. A hurricane keeps the name it received as a tropical storm. Our guide on how hurricanes are named covers the lists and retired names.
Why is it called a typhoon or a cyclone in other places?
The only difference is location. The NOAA National Ocean Service says the term hurricane is used in the North Atlantic, central North Pacific and eastern North Pacific, and the same kind of storm in the Northwest Pacific is called a typhoon. In the South Pacific and Indian Ocean, the generic term tropical cyclone is used regardless of wind strength. NHC’s glossary draws the Pacific line at the International Date Line: hurricane to the east, typhoon to the west, north of the equator.
| Ocean area | Term for a storm of 74 mph or more | Center that names storms |
|---|---|---|
| North Atlantic, Caribbean Sea and the Gulf | Hurricane | NHC, Miami |
| Eastern North Pacific (east of 140°W) | Hurricane | NHC, Miami |
| Central North Pacific (140°W to the Date Line) | Hurricane | Central Pacific Hurricane Center, Honolulu |
| Western North Pacific and South China Sea | Typhoon | RSMC Tokyo |
| North Indian Ocean (Bay of Bengal, Arabian Sea) | Tropical cyclone | RSMC New Delhi |
| South Pacific and south Indian Ocean | Tropical cyclone | Other WMO regional centers |
NHC adds that in the western North Pacific, the term super typhoon is used for storms with sustained winds above 150 mph.
Why do agencies report different wind speeds for the same storm?
Agencies average the wind over different periods. NHC uses a 1-minute average. The World Meteorological Organization’s Global Guide to Tropical Cyclone Forecasting gives the WMO standard as the maximum 10-minute sustained wind at 10 meters. A 10-minute average comes out lower than a 1-minute average for the same storm, so a storm near the 74 mph line can count as a hurricane under one averaging method and a tropical storm under the other.
What happens when a hurricane weakens or loses its tropical features?
NHC changes the label as the storm changes. A post-tropical cyclone is a former tropical cyclone that no longer has enough tropical characteristics, and NHC says it can still bring heavy rain and high winds. A remnant low is a post-tropical cyclone without organized thunderstorms and with winds below 34 knots (39 mph). An extratropical cyclone has shifted to drawing energy from temperature contrasts, and NHC notes it can still have hurricane or tropical storm force winds. The National Weather Service can issue land watches and warnings for post-tropical cyclones that still threaten land.
A storm keeps its name if it crosses from one ocean basin into another while still a tropical cyclone, under the U.S. National Hurricane Operations Plan.
Bottom line
Depression, storm and hurricane are wind stages of one type of system: 38 mph or less, 39–73 mph, and 74 mph or more. Typhoon and tropical cyclone are regional names for the same thing. Tropical storms and post-tropical systems can still cause deaths and damage, so follow NWS alerts and your local officials whenever any tropical system approaches.
FAQ
Can a tropical storm be dangerous?
Yes. NHC’s 2026 Atlantic season table lists Tropical Storm Arthur with peak winds of 50 knots (about 60 mph), one direct death and about $700 million in U.S. damage. NHC issues tropical storm watches and warnings for sustained winds of 39–73 mph.
What is the difference between a typhoon and a super typhoon?
Both are western North Pacific storms with sustained winds of at least 74 mph. NHC notes that the term super typhoon is used there when sustained winds exceed 150 mph.
What do the letters D, S, H and M mean on NHC maps?
On the NHC cone graphic, D is a tropical depression (under 39 mph), S a tropical storm (39–73 mph), H a hurricane (74–110 mph) and M a major hurricane (over 110 mph). Our guide on reading the NHC forecast cone explains the rest of the map.
Does a storm get a new name if it crosses into the Pacific?
Not if it stays a tropical cyclone. The National Hurricane Operations Plan says the name is kept when a tropical cyclone passes from one basin into another with continuous advisories.