After a year of record warm global temperatures caused by climate change and an El Niño weather pattern, “a weak La Niña” is expected to form before the arrival of winter, the National Weather Service said, and could last until March next year. .

For much of the country, the relative weakness of the coming La Niña, which has a 60% chance of forming in November, will not result in winter temperatures above or below average, the National Oceanic and Atmospheric Association said in a long-term forecast. released on Thursday. But temperatures are expected to be above normal throughout the south. The Pacific Northwest and upper Great Plains states are expected to experience colder than average temperatures.

“NOAA predicts wetter-than-average conditions for the entire northern continental U.S., particularly in the Pacific Northwest and the Great Lakes region, along with northern and western Alaska,” the agency said on its website. “Meanwhile, drier than average conditions are expected in the Four Corners region from southwest to southeast, the Gulf Coast and the lower mid-Atlantic states.”

While the arrival of La Niña could bring drought relief to the Ohio River Valley, other areas with dry conditions won’t be so lucky.

“Unfortunately, after a brief period in the spring of 2024 with minimal drought across the country, more than a quarter of the landmass in the continental U.S. is currently in at least moderate drought,” said Brad Pugh, drought operations lead at NOAA , said in a press release. “And the outlook for winter precipitation does not bode well for widespread relief.”

The difference between El Niño and La Niña

The interplay between the two weather patterns typically translates into warmer temperatures during an El Niño event and colder weather during La Niña.

“During normal Pacific Ocean conditions, the trade winds blow westward along the equator, bringing warm water from South America to Asia,” NOAA says on its website. “To replace that warm water, cold water rises from the depths – a process called upwelling. El Niño and La Niña are two opposing climate patterns that break these normal conditions.”

But because forecasters predict a weaker and potentially short-lived La Niña, it will be “less likely to result in conventional winter impacts.”

Implications for the 2025 hurricane season

Because the jet stream pushes north during La Niña events and weakens it over the Pacific Ocean, that pattern could result in warmer-than-normal temperatures in the southern U.S. and “lead to a more severe hurricane season,” NOAA said.

That’s not welcome news for parts of the country still struggling to recover from Hurricanes Helene and Milton.

“During La Niña events, atmospheric conditions are generally more favorable for the formation and intensification of hurricanes in the Atlantic Basin,” the Florida Oceanographic Society says on its website. “The absence of strong wind shear allows hurricanes to develop more easily and strengthen, increasing the likelihood of landfall in Florida and the Gulf Coast.”

Climate change and the El Niño/La Niña cycle

Although the fluctuations between El Niño and La Niña can lead to dramatic weather changes, they are driven by a steady increase in global temperatures caused by greenhouse gas emissions.

“If you look at a graph of Earth’s average surface temperatures over time, you see a steady increase due to increasing concentrations of greenhouse gases in the atmosphere, but then you see ups and downs every few years,” says Michael McPhaden, a senior researcher. scientist at NOAA. “The ups are El Niño and the downs are La Niña.”