For months, the El Niño weather system has been contributing to higher-than average temperatures. There’s a good chance that a new system – La Niña – will move in by the end of summer.
Here’s what we can expect from it.
According to a May 9 update from the National Oceanic and Atmospheric Administration, a transition from El Niño to neutral conditions is expected in this next month. Then, “La Niña may develop in June-August (49% chance) or July-September (69% chance),” said NOAA.
Below-average equatorial sea surface temperatures (SSTs) recorded last month in small regions of the Pacific Ocean are one signal that La Niña is arriving.
Both weather systems are naturally occurring. While El Niño refers to a warming of the ocean surface, per the U.S. Geological Survey, La Niña has an opposite effect according to the NOAA. With it comes strong trade winds that push warm water towards Asia.
“Off the west coast of the Americas, upwelling increases, bringing cold, nutrient-rich water to the surface,” the NOAA explained.
During El Niño periods, marine life off the Pacific coast is strongly impacted since that upwelling weakens with warmer temperatures. A lack of nutrients results in reduced phytoplankton, which many fish feed on.
“The warmer waters can also bring tropical species, like yellowtail and albacore tuna, into areas that are normally too cold,” NOAA said.
In a February interview with Audacy station KNX in Los Angeles, NOAA scientist Nat Johnson said that El Niño had already peaked. He also said that it was one of the strongest El Niño systems on record.
Although NOAA said some below-average temperatures have been recorded recently, it noted that “above-average SSTs prevailed across the rest of the equatorial Pacific,” of the latest recordings. Overall, weather conditions did indicate that El Niño was weakening.
“The most recent IRI plume favors an imminent transition to ENSO-neutral, with La Niña developing during July-September 2024 and then persisting through the Northern Hemisphere winter,” said NOAA. It added that “La Niña generally tends to follow strong El Niño events, which also provides added confidence in the model guidance favoring La Niña.”
As La Niña brings nutrient-rich water to the surface in the ocean, it also typically brings dry weather to the Southern U.S. and increases the risk of drought there. In the Pacific Northwest and Canada, there is a chance of heavy rain and flooding. La Niña years in the U.S. are also marked by winter temperatures that are warmer than normal in the South and cooler than normal in the North.
When it comes to storms, La Niña can also usher in a more severe hurricane season than usual. According to research from Colorado State University, “the 2024 Atlantic basin hurricane season will be extremely active,” with the transition from El Niño to La Niña.