(Bloomberg) -- Hurricane Milton’s surge to Category 5 strength comes from high-temperature Gulf of Mexico waters that also intensified the deadly Helene less than two weeks ago, contributing to the new storm’s odd west-to-east track that threatens Tampa, Florida.

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“There is really no historical precedent for a track like this,” said Ryan Truchelut, president of commercial forecaster WeatherTiger.

Though the calendar says October, the water is 86F (30C) in Mexico’s Bay of Campeche, where Milton is gathering strength, and nearly that warm off Tampa, according to the National Data Buoy Center. Hurricanes draw power from hotter water, which acts as fuel for storms.

“The Gulf is still being summer-like with water temperatures,” Truchelut said. Gulf waters averaged 78.4F in October 2023, according to the website seatemperature.info.

The balmy water has allowed Milton to rapidly intensify as it moves across the Gulf toward Florida’s west coast, where it’s forecast to make landfall Oct. 9. A storm rapidly intensifies when its winds grow in strength by 35 miles per hour or more in 24 hours. Milton met the definition in 12 hours Sunday, according to US National Hurricane Center records, and has now reached the top rung of the five-step Saffir-Simpson scale with 175 mile-per-hour winds, the strongest Atlantic storm of 2024.

“Milton has gorged itself on the insanely warm waters of the Gulf of Mexico, converting that heat and moisture-laden air into ferocious winds, copious rainfall, and inundating storm surge,” said Jennifer Francis, a senior scientist at the Woodwell Climate Research Center. “The heat comes from decades under an extra-thick blanket of greenhouse gases, put there by humans burning fossil fuels.”

While the larger weather patterns pushing west to east aren’t unusual in October, what is odd is the warm water that is sustaining such a powerful storm on this path. Depending on where along the coast it strikes, Milton has the potential to be the worst hurricane to hit Tampa since 1921.

In recent years, most hurricanes striking western Florida have come from the western Caribbean or southern Gulf and then hit the coastline at an angle. Milton will be coming straight across like a hammer hitting an anvil.

Beating Helene

The heat in the Gulf is so strong it managed to shake off the effects of Hurricane Helene.

Helene, the deadliest US hurricane since Maria in 2017, killed at least 225 people across the South. It moved over the eastern Gulf of Mexico on its way to a Sept. 26 landfall in Florida as a Category 4 storm.

Usually, when such a powerful storm passes over the ocean it churns up cold water from the depths that cools the surface, robbing the next storm of some power. Helene only dropped temperatures in the region about 1F to 3F, and they’ve quickly rebounded.

“That minimal change is likely due to the warm waters being very deep, and Helene moving quickly — about 25 mph — as it passed over,” Truchelut said.

Across the entire Gulf of Mexico, water temperatures are running anywhere from 1F to nearly 5F above normal, said Isaac Longley, a meteorologist with AccuWeather Inc. Milton is crossing the warm Loop Current in the Gulf of Mexico before it reaches Florida, a patch of water that also boosted Hurricane Helene as it neared the state.

The Loop Current is an area of warm water that travels up from the Caribbean into the Gulf of Mexico, then exits via the Florida Straits and flows into the Gulf Stream.

Globally, ocean water temperatures have been setting records for more than a year. This has led to explosive growth by typhoons and hurricanes, and has also fueled deadly floods and heat waves in Europe, Asia and North America.

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“It is not to be taken lightly,” said Brandon Buckingham, a meteorologist with commercial forecaster AccuWeather Inc.

(Updates with scientist’s evaluation in sixth paragraph)

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