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 by March of next year, according to the National Weather Service could last.

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

“NOAA forecasts wetter than average conditions across the northern portion of the continental U.S., particularly in the Pacific Northwest and Great Lakes region, as well as northern and western Alaska,” the agency said on its website. “Meanwhile, drier than average conditions are expected from the Four Corners region in the Southwest to the 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 suffering from dry conditions will not be so lucky.

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

The difference between El Niño and La Niña

The interaction of the two weather patterns typically results in warmer temperatures during an El Niño event and colder weather during La Niña.

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

However, with meteorologists predicting a weaker and potentially short-lived La Niña, it is “less likely to result in traditional winter impacts.”

Impact on the 2025 hurricane season

As the jet stream pushes north during La Niña events, weakening it over the Pacific, this pattern can lead to warmer than normal temperatures across the southern U.S. and “result in 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 tend to be more conducive to the formation and intensification of hurricanes in the Atlantic basin,” the Florida Oceanographic Society says on its website. “The lack of strong wind shear allows hurricanes to develop and strengthen more easily, increasing the likelihood of landfall in Florida and the Gulf Coast.”

Climate change and the El Niño/La Niña cycle

While the fluctuations between El Niño and La Niña events can lead to dramatic weather changes, the cause of this lies in the steady increase in global temperatures caused by greenhouse gas emissions.

“If you look at a graph of global average surface temperatures over time, you see a steady increase due to rising greenhouse gas concentrations in the atmosphere, but then you see peaks and troughs every few years,” said Michael McPhaden, a senior scientist at the NOAA. “The highs are El Niño and the lows are La Niña.”