El Niño and Hurricanes

• Heat: A thick layer of very warm ocean water; 
• Instability: atmospheric conditions that allow air to rise – typically, warm and humid near the surface and cooler aloft;  
• Low wind shear: little change in the speed or direction of the wind between the surface and higher altitudes 

Hurricanes impact human health, activities, and economies. Strong winds and heavy rainfall cause power outages and road closures and damage and destroy homes and businesses. High winds during Hurricane Idalia in 2023 caused significant impact on Florida agriculture, destroying crops, killing livestock, and damaging equipment. Heavy rains during 2018’s Hurricane Olivia caused flash flooding that moved some buildings off their foundations and inundated others in Maui. In Honolulu, flash flooding trigged a 32,000-gallon sewer discharge into Honolulu Harbor. Sea-level, storm surge and waves: Coastal areas can experience heavy surf and storm surge driving oceanwater inland. This can damage coastal infrastructure, from piers to ports, and disrupt shipping, fisheries, and recreation. In 2020 (a La Niña year), Hurricane Laura drove a coastal surge of up to 18 feet, enough to reach the attic of a two-story house, along the Louisiana coast. Saltwater inundation extended 35 miles or more inland in some places.  Nor does a storm have to make landfall to cause damage. In 2014, Hurricane Marie did not make landfall on the Pacific Coast, but high waves damaged infrastructure along the Southern California coast, including at the Port of Long Beach and in Channel Islands National Park. Data about individual hurricanes and their impacts can be found at https://www.nhc.noaa.gov/data/tcr/index.php. 

Ex-typhoons: Hurricanes can even have impacts well outside the tropics. In 2022, a La Niña year, Typhoon Merbok transitioned into a mid-latitude storm and traveled north to western Alaska, flooding numerous villages. In October 2025, another hurricane-fed storm, ex-Typhoon Halong, impacted coastal Alaska. 
 

The El Niño-Southern Oscillation involves natural shifts in ocean temperatures, trade winds, and rising air in the tropical Pacific that occur on a roughly 3–7-year timescale. Normally, trade winds, which blow from the east to the west in the tropics, push the warmest water in the Pacific Ocean toward Indonesia, while upwelling of cold water that flows north along the coast of South America keeps surface ocean temperatures in the eastern Pacific low. During an El Niño event, the location of the warmest water in the tropical Pacific shifts to the east, creating a thick layer of warm water that extends across much of the tropical Pacific Ocean. This weakens the Pacific trade winds near the surface and shifts the location of convention and thunderstorms further east than normal. El Niño can influence the tropical Atlantic, as well, increasing wind shear in the region.  

During El Niño, the thick layer of warm seawater and low wind shear in the Pacific create conditions favorable to hurricane formation. In the Atlantic Ocean, however, greater wind shear means conditions are less conducive to hurricanes forming.  

Since 1991, observations suggest that during strong El Niño events, the Atlantic has had fewer hurricanes and major hurricanes than normal. The Pacific, especially the eastern Pacific, has had more than usual. But there are some key differences.  For example, the 1991–1992 El Niño started a little later in the year and strengthened more slowly than the 1997 or 2015 El Niños. However, it lasted well into the summer of 1992, while the 1997–1998 and 2015–2016 El Niños ended in the spring.