Climate experts issue major update to La Niña forecast

In its latest forecast on Thursday, the Climate Prediction Center said a La Niña weather pattern is expected to arrive this winter, but that it may not have much of an impact after all.

La Niña occurs when sea waters in the equatorial eastern Pacific Ocean become at least half a degree cooler than average. This is the opposite of El Niño, when the same waters become warmer than average.

This year, La Niña is expected to officially begin sometime between now and November. There is a 77% chance that La Niña will continue into winter (December-February), but it is not expected to last long beyond 2025.

The Climate Prediction Center described the current La Niña outlook as “weak and short-lived” and said it would influence future winter forecasts.

Weak La Niña impacts winter

La Niña typically makes North American winter patterns relatively predictable, but the strength of La Niña affects that predictability.

A typical La Niña event means drier, warmer weather for most southern states, including California, while many northern states will experience wetter, cooler weather because the Pacific jet stream is further north than normal.

But a weakening La Niña “will make traditional winter impacts less likely, although predictable signals may still influence forecast guidance,” according to the latest outlook.

That means the winter outlook will only broadly resemble the map above: Southern states may still be dry and warm, but not necessarily too far off average. Similarly, the Pacific Northwest and Ohio Valley may see wetter than normal conditions, but the forecast is murky.

A weakening La Niña essentially means that without the usual influence of a strong El Niño or a strong La Niña, it may become more difficult to establish the accuracy of winter forecasts.

When will La Niña end?

This “short-lived” La Niña event is expected to begin between September and November and strengthen through the winter.

But it's likely to be gone already by early next year, and the Climate Prediction Center thinks it could be over by spring of 2025.

We can't say much more than that yet. The odds of an El Niño event materializing increase toward late spring 2025, but remain low overall.