9 Facts About Hurricanes You Probably Don't Know

Hurricanes must meet a minimum wind speed.

Hurricanes can only be called hurricanes when wind speeds exceed 119 kph (74 mph). This is classified on a scale called the Saffir-Simpson Hurricane Wind Scale, and it has five categories, or levels, with category one being the weakest and category five the strongest. The scale is as follows:

• Category 1: Wind speed 74-95 mph. Some damage will occur. 
• Category 2: Wind speed 96-110 mph. Extensive damage will occur. 
• Category 3: Wind speed 111-129 mph. Devastating damage will occur. 
• Category 4: Wind speed 130-156 mph. Catastrophic damage will occur. 
• Category 5: Wind speed >157 mph. Catastrophic damage will occur.

There are also two non-hurricane classifications:

• Tropical storm: Wind speed 39-73 mph
• Tropical depression: Wind speed <38 mph

Hurricanes form only in certain meteorological conditions.

Hurricanes form when warm air over the ocean rises at a rapid rate, creating an area of low pressure. This air cools and condenses, forming massive clouds and sometimes thunderstorms, which then continue to be fueled by more rising warm air. Because of the Earth's rotation, strong winds spiral inwards and then upwards, drawing in more warm air and moisture. The wind speeds up at a phenomenal rate until it reaches one of the categories above. As soon as it does, the hurricane is named and tracked via NOAA.

It's important to note that hurricanes can intensify over time and become stronger. They can also weaken as they approach the coast. This is because hurricanes need the constant fuel of water to keep going. When a hurricane makes landfall, it's usually an incredibly powerful storm that can sustain itself before heading back up the coastline.

In some cases, hurricanes can travel from the Caribbean to the East Coast and then intensify and boomerang back towards Europe. During Hurricane Erin in 2025, a warm water anomaly near Iceland actually fueled the hurricane to an area where hurricanes typically wind down. This sent an incredibly powerful pulse of swell to western Europe and beyond. It just goes to show that subtle changes to the ocean can have a massive impact on the longevity of hurricanes.

Hurricanes can produce long-period swells.

Most hurricanes are accompanied by long-period swells before and often after the storm hits. This is because the storms sometimes form thousands of miles out to sea and travel uninterrupted across the ocean's surface. The distance between waves is greater due to the storm being further away. If you see the period on a forecast chart jump to 19, 20, 21-plus seconds, odds are it's from a hurricane.

The "biggest" hurricane depends on what you mean.

Curious about the biggest hurricane in history? The answer really depends on what you mean by the term "biggest." If we're talking about maximum sustained wind speed, then Hurricane Patricia (2015) holds the world record for highest wind speed, reaching 254 mph. However, if you're measuring by atmospheric pressure, then Super Typhoon Tip (1979) holds the record, with pressure dropping as low as 870 millibars.

When a hurricane rapidly intensifies, it's called a bomb cyclogenesis.

"Bomb cyclogenesis" may sound like a fancy term, but it simply refers to when a hurricane rapidly intensifies. It is measured by the central low pressure dropping at least 24 millibars within 24 hours.

This term isn't to be confused with the recently popularized term "weather bomb," which is widely used to signify any extreme weather event.

The "calm before the storm" is an actual thing.

No doubt you've heard the phrase "the calm before the storm." Turns out there's actually some truth to it. For certain storms (though not all), there can be a period before the storm hits where meteorological conditions are surprisingly calm and quiet. This can occur if a low-pressure area is created when warm, moist air is being pulled into an impending storm system. The resulting low-pressure area is warm and dry—producing a calm moment before the storm.

Hurricane season is six months long.

In the Atlantic basin, the hurricane season runs from June 1 to November 30. This is when hurricanes are most active in the Atlantic, and coastal communities are on high alert. Robust monitoring systems are in place to track each hurricane so that affected communities have the opportunity to take safety precautions. Forecasting websites also track the swell, so that surfers know where to go when these powerful storms sweep in.

Hurricane preparedness is critical.

The easiest way to stay safe in a hurricane is to move away from the storm; however, this is not always feasible. Secure your home by boarding windows and doors, and reinforcing your roof if you can. If it seems safe, you can hunker down and wait it out—but be sure to follow any evacuation orders that have been issued by your local or state government. Even after the immediate danger of a hurricane has passed, secondary problems such as flooding, power outages, mold and contamination, etc., can cause further devastation for local communities.