There is a 60 percent chance of a La Niña event happening this year, which could last until March 2025.

La Niña is part of a climate cycle that causes extreme weather changes around the world, the effects of which vary from place to place. It is the cool phase of the El Niño-Southern Oscillation that causes changes in wind and ocean temperatures in the Pacific Ocean.

During an El Niño (which means “little boy” in Spanish), the trade winds that normally blow across the Pacific Ocean toward Asia weaken, causing warm ocean waters to build up on the western edge of the Americas. However, in La Niña (“little girl”), these trade winds become stronger, bringing cold water from the depths of the ocean to the surface (a process called “upwelling”), causing cooler temperatures in the eastern part of the Pacific. These colder temperatures then influence the position of the jet stream – a strong nuclear wind that blows across the planet from west to east – which is pushed further north.

Once this shift in the jet stream occurs, storms become wetter as they absorb more moisture from the ocean. This tends to cause more droughts in the southern US and heavy rains and floods in the Pacific Northwest and Canada. La Niña can also lead to more severe hurricane seasons.

In general, El Niño is more common than La Niña, but between 2020 and 2023 the world witnessed a rare “triple-dip” La Niña event.

“We had three consecutive winters where we had La Niña conditions, which was unusual because the only other instance of this happening was between 1973 and 1976,” said Michelle L’Heurex, a climate scientist at the National Oceanic and Atmospheric Administration. NOAA) Climate Prediction Center, told AP.

While it appears a fourth La Niña event is on the way, forecasters believe it will be a weaker event as it appears to be developing later in the season than normal. However, many models seem to indicate that it is coming.

“As a result of the warmer forecasts and the recent weakening of equatorial trade winds, the team is still in favor of a weak event but has lowered the chances of La Niña,” NOAA explains. “A weaker La Niña implies it is less likely to result in conventional winter impacts, although predictable signals could still influence forecast guidance.”

“In summary,” they say, “La Niña is favored to emerge in September-November (60 percent chance) and is expected to persist until January-March 2025.”