Hawaii has had more than its fair share of storms this season. First, there was Hurricane Fausto in July. Then there were Hurricane Lala and Tropical Storm Moke in August and most recently, Hurricane Lowell, which grazed the western part of the archipelago this week.

Meanwhile, in the Atlantic, the season has been strangely uneventful. In fact, the Atlantic hasn’t seen any hurricanes all season. If the trend holds past September 12, it will be historic: Any hurricanes that form after that date will be the latest first hurricane since 1966, when we started keeping track. Whether a hurricane will form at all is still up in the air.

So what gives? Why is the Pacific teeming with hurricanes while the Atlantic remains so chill?

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Hurricane activity very close to Hawaii is typically rare, thanks to strong trade winds and cooler waters protecting the archipelago. In fact, in the past 75-plus years, only six hurricanes had ever come within 50 miles of the main Hawaiian Islands before this hurricane season, says meteorologist and hurricane specialist Michael Lowry. And during this time, Hurricanes Dot and Iniki, in 1959 and 1992, respectively, were the only hurricanes to make a direct hit on the islands, he adds.

There are a few reasons why this season has been so starkly different. For one, this year is shaping up to produce an especially powerful El Niño, a cyclic climate pattern that affects weather patterns around the globe.

“El Niño events typically help limit how many hurricanes can develop in the Atlantic and help provide ideal conditions for hurricanes in the eastern and central Pacific,” says Nicholas Grondin, an assistant professor in environmental studies at the University of Tampa.

The reason why has to do with ocean temperatures and something called “vertical wind shear,” a metric used to describe the change in wind speed and direction with altitude.

Specifically, El Niño is characterized by warmer-than-usual water in part of the Pacific between five degrees South and five degrees North, or “narrowly along the equator,” explains Matthew Rosencrans, lead hurricane season forecaster at the National Weather Service. Warmer oceans fuel hurricanes.

Right now sea surface temperatures in the East Pacific are “well above normal” all the way up to 20 degrees North—about the latitude of Hawaii, he says.

On top of that, there has been notably low vertical wind shear in the Pacific, explains Phil Klotzbach, a senior research scientist at Colorado State University. High wind shear can destabilize hurricanes and other cyclones, while low wind shear makes them more likely.

In the part of the Pacific near Hawaii, vertical wind shear has been “well below normal,” Klotzbach says—and this means ideal hurricane conditions.

In parts of the Atlantic, however, vertical wind shear has been high, creating “hostile” conditions for hurricanes, Grondin says. If a cyclone manages to form at all, the storms often “stay weak and decay quickly,” he says, just like Tropical Storm Dolly did last month.

A quiet year does not mean no hurricanes, however, Grondin says. September may be the usual peak of Atlantic hurricane season, but it’s far from the end. “Just because nothing is developing right now does not mean nothing will develop between now and the end of the season,” he adds.

In August, in fact, federal meteorologists predicted a “below normal” Atlantic hurricane season, with between two and six hurricanes expected to form in the Atlantic.