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Come summer in the United States, those on the East Coast eye the Atlantic warily. Atlantic hurricane season usually runs from June 1 to November 30, normally peaking in September. However, over the past decade, that is no longer the norm. At least one named storm has formed before June 1 in seven of the last 10 years. This had only happened three times between 2005 and 2014.

In a recent study, researchers found that the probability of major hurricanes occurring had increased by about 22% from 1979 until 2017. They are also becoming stronger faster, a phenomenon known as “rapid intensification”.

For example, before Hurricane Helene struck Florida in September 2024, it grew from a Category 1 to a Category 4 hurricane in a single day. Usually that change is more gradual, happening over several days.

And when that happens close to landfall, it means less time to prepare and evacuate, posing a major risk to coastal communities.

Meanwhile, recent research shows that hurricanes are travelling more slowly, which brings more damage caused by strong winds and a higher risk of flooding, as more rain is dumped over a particular area.

Warmer oceans, faster hurricanes

The formation and intensity of tropical cyclones depend on just the right mix of environmental conditions. Essentially, it comes down to the amount of fuel available.

As our climate continues to grow warmer, so do the oceans, which absorb 90% of the world’s surplus heat. The hotter the water, the more energy available to power the storm’s growth. A warmer atmosphere can also hold more moisture, which in turn means more fuel for the tropical systems.

Usually, as the hurricane swirls, it brings cooler water from the bottom to the surface of the ocean, but if deep waters are also warm, hurricanes intensify faster.

Another consequence of global warming is rising sea levels, which makes so-called storm surges (and therefore, flooding), worse. With Hurricane Katrina, for example, it was the strong storm surge coupled with engineering mistakes that caused levees to fail, devastating the New Orleans area.

Read moreClimate change amplified intensity of Hurricane Helene, study says

What does the future hold?

According to the US National Oceanic and Atmospheric Administration (NOAA), the global number of tropical cyclones may decrease or remain unchanged in the future, but the proportion of stronger Category 4 or 5 storms is projected to increase.

They are also more likely to become more intense and have higher rainfall rates than present-day hurricanes.

“If we fix a threshold in terms of wind, how we define a major hurricane, then the number of hurricanes that go above this threshold is increasing, although the total number is the same. And the proportion of Category 4 and 5 tropical cyclones is going to increase even more if we don’t stop burning fossil fuels,” says Davide Faranda, research director at France’s National Centre for Scientific Research.

Then there are other risks, Faranda says. “For example, consecutive cyclones – cyclones that are one after the other, [and] you cannot recover from the first [before] the second one.”

And other damaging events can follow tropical cyclones, for example heatwaves. If a hurricane hits Florida with a lot of moisture and flooding, and then you have a heatwave, people will still be reeling from the hurricane when they are hit by the extreme heat conditions that follow.

Research also indicates that the geographical range of hurricanes and tropical cyclones will increase, meaning millions more people could face the devastating damage of these storms in the years to come. Economic damage from such storms is expected to double every generation because of population growth, inflation and expanded infrastructure along the coast.