La Niña has officially started: What happens next

AUSTIN (KXAN) -- The Climate Prediction Center announced Thursday that La Niña has officially started. A detailed analysis found La Niña began in December 2024 with a weak La Niña favored during the rest of this winter.

La Niña is the cool phase of ENSO (El Niño-Southern Oscillation) that is marked by sea-surface water temperatures 0.5ºC below the climatological average in a key area of the eastern Pacific.

Those water temperatures reached that key metric in December marking the long-awaited arrival of La Niña.

La Niña typically has the greatest impacts on the Northern Hemisphere in the winter season as the jet stream or storm track is pushed farther north, keeping it cooler in the Pacific Northwest and Upper Midwest, whereas warmer and drier temperatures are more common in the southern states.

As I write this much of the south is dealing with or bracing for winter weather. The La Niña pattern doesn't mean it won't get cold, wet or wintry -- but rather winter typically is warmer and drier for southern areas.

How long will La Niña last?

This is expected to be a short-duration La Niña with an ENSO Neutral pattern (neither cool or warm phase) expected to return in the March-May period.

Last winter (2023-2024) was an El Niño winter marked by cooler and wetter weather for the southern states.

What about the rest of 2025?

While forecasting climate patterns like ENSO, they become more complicated before the spring season is completed.

The odds favor ENSO Neutral conditions to continue through summer and into next fall. While Neutral is favored, the odds of another La Niña are substantially higher than the return of El Niño as we head through the fall months.