The Difference Between a Tropical Storm Vs Hurricane
When it comes to powerful weather systems, it’s common to wonder about the difference between a tropical storm and a hurricane. They are closely related because they both develop from tropical cyclones, which are storm systems that form over warm ocean water.
The main difference comes down to wind speed. A tropical storm has maximum sustained winds of 39 to 73 mph. A hurricane has maximum sustained winds of 74 mph or higher.
Still, both can bring dangerous conditions, including heavy rain, flooding, rough surf, rip currents, power outages, and coastal impacts. Here’s what to know before the next storm shows up in the forecast.
Tropical Storm vs. Hurricane: What They Have in Common
Tropical storms and hurricanes both need warm ocean water, moisture, and favorable atmospheric conditions to develop. Warm water helps fuel these systems by causing air above the ocean to rise, creating lower pressure near the surface.
As warm, moist air rises and cools, it condenses into clouds and thunderstorms. That process releases heat, which can help the storm strengthen if conditions remain favorable.
Tropical cyclones often form over warm waters in tropical and subtropical regions. In general, sea surface temperatures around 80°F or warmer can support development, though other factors also matter, including wind shear, moisture, and the storm’s organization.
It Often Starts as a Tropical Depression
Before a system becomes a tropical storm or hurricane, it may first be classified as a tropical depression.
A tropical depression is a tropical cyclone with maximum sustained winds of 38 mph or less. At this stage, the system may still be relatively weak, but it is organized enough for forecasters to track.
This is often the first sign that something may be developing, especially during Atlantic hurricane season.
What Is a Tropical Storm?
A tropical depression becomes a tropical storm when maximum sustained winds reach 39 to 73 mph.
At this point, the storm is given a name, making it easier for forecasters, emergency officials, and the public to track.
Tropical storms can bring:
Strong winds
Heavy rain
Flash flooding
Coastal flooding
Rough surf
Rip currents
Isolated tornadoes
While tropical storms are weaker than hurricanes by wind speed, they can still be dangerous. A slow-moving tropical storm can drop enormous amounts of rain and cause serious flooding, even if it never becomes a hurricane.
Tropical storms also can strengthen quickly when conditions are favorable. That is why it is important to monitor official forecasts and not assume a tropical storm will stay weak.
Can a Tropical Storm Become a Hurricane?
Yes. A tropical storm becomes a hurricane when maximum sustained winds reach 74 mph or higher.
This can happen gradually over several days, or more quickly if the storm moves over very warm water with low wind shear and plenty of moisture.
A good example is Hurricane Hilary in 2023. Hilary strengthened into a Category 4 hurricane over the eastern Pacific before weakening. It later made landfall in Mexico’s Baja California as a tropical storm and brought historic rainfall and flooding concerns to parts of Southern California.
That kind of storm history is a reminder that tropical systems can change quickly. A storm does not have to make landfall as a major hurricane to cause dangerous impacts.
What Is a Hurricane?
A hurricane is a tropical cyclone with maximum sustained winds of at least 74 mph.
Hurricanes are rated using the Saffir-Simpson Hurricane Wind Scale, which ranks storms from Category 1 to Category 5 based only on sustained wind speed.
Here are the official hurricane categories:
Category 1: 74 to 95 mph
Category 2: 96 to 110 mph
Category 3: 111 to 129 mph
Category 4: 130 to 156 mph
Category 5: 157 mph or higher
Category 3, 4, and 5 hurricanes are considered major hurricanes because of their potential for significant wind damage and loss of life.
However, the category number does not tell the whole story. The Saffir-Simpson scale measures wind only. It does not measure storm surge, rainfall flooding, tornado risk, or storm size.
Hurricane Structure
Hurricanes are usually more organized than tropical storms.
A strong hurricane may develop a visible eye at its center. The eye is often relatively calm, but it is surrounded by the eyewall, where the strongest winds and heaviest rain are typically found.
The eyewall is usually the most intense part of the hurricane. If it moves over land, it can cause severe wind damage in a short period of time.
Not every hurricane has a perfectly clear eye, and not every tropical storm lacks organization. Still, a well-defined eye is one of the classic signs of a stronger tropical cyclone.
Can a Hurricane Weaken Back Into a Tropical Storm?
Yes. Hurricanes can weaken back into tropical storms if they move over cooler water, encounter dry air, face stronger wind shear, or move over land.
This weakening can bring some relief, especially from wind threats, but it does not mean the storm is harmless. A weakening tropical system can still produce flooding rain, storm surge, dangerous surf, and tornadoes.
Tropical Storm Don in 2023 is one example of a system that briefly reached hurricane strength before weakening again.
Key Differences Between Tropical Storms and Hurricanes
The biggest difference between a tropical storm and a hurricane is wind speed.
A tropical storm has sustained winds between 39 and 73 mph. A hurricane has sustained winds of 74 mph or higher.
Other differences include:
Wind Speed
Tropical storms are weaker by wind speed, while hurricanes have stronger sustained winds and are ranked by category.
Structure
Tropical storms can be organized, but hurricanes are often more developed and may have a defined eye and eyewall.
Damage Potential
Tropical storms can cause flooding and localized damage. Hurricanes can cause more severe wind damage, especially at Category 3 strength or higher.
Storm Surge
Storm surge is a major concern with hurricanes, but it can also happen with strong tropical storms. Coastal residents should always follow local evacuation guidance, regardless of category.
Forecast Attention
Both tropical storms and hurricanes deserve close attention. A tropical storm can strengthen, and a weakening hurricane can still bring dangerous impacts.
Stay Safe and Remain Vigilant
The difference between a tropical storm and a hurricane mostly comes down to wind speed, but safety is about more than a number.
Tropical storms can flood neighborhoods. Hurricanes can damage homes and knock out power. Both can make roads dangerous, threaten coastal communities, and change track or intensity faster than expected.
The best thing you can do is monitor trusted weather updates, know your evacuation zone, prepare emergency supplies, and take local warnings seriously.
Weather changes fast, so help your community stay prepared. Share this story with friends, family, or your group chat, and keep your forecast in the now with Weather Forecast Now.