After months of uncertainty, La Niña is officially here. Here’s what it means in western WA
It took longer than expected, but on Thursday, Jan. 9, the National Oceanic and Atmospheric Administration declared that the criteria for the La Niña weather pattern have been met. The phenomenon, characterized by the cooling of the equatorial Pacific, can impact the weather across much of the world. But even though the criteria have been met, this year’s La Niña could have less of an impact than usual.
So what does it mean for western Washington? Here’s what we know.
Weak La Niña pattern expected
In order for La Niña to emerge, surface temperatures in the Niño 3.4 region of the equatorial Pacific have to see an average temperature more than 0.5 degrees Celsius below normal for five straight overlapping three-month stretches. The pattern was expected to take shape in late 2024 at first but was slow to develop.
According to Jeff Michalski, a meteorologist with the National Weather Service in Seattle, part of the reason La Niña arrived so late is because the phenomenon is weaker than usual this year. As a result, its impacts aren’t expected to be quite as pronounced, and it likely won’t last as long as usual.
“It is a weak La Niña pattern,” Michalski told McClatchy in a phone call. “It’s based on the cooling of the waters and the equatorial Pacific. And there are certain thresholds to meet before classifying whether or not it is classified as an El Niño, a neutral or a La Niña.”
More rain, colder temperatures in WA
So what can Washington expect this winter? According to Michalski, La Niña winters tend to be colder and rainier in the western part of the state than a typical winter.
“Based on climatology, looking back over the last 30 years, La Niña weather patterns, the favored effects in western Washington are for wetter than average and cooler than average conditions through the winter period,” Michalski said.
The phenomenon also brings a higher chance of snowfall in the mountains, according to Michalski, although it’s not a guarantee.
How long will La Niña last?
While Washington could see some effects of La Niña, they aren’t expected to last very long.
“We see most of the effects of La Niña and El Niño during the winter weather months, where the [changes in] air and sea surface temperatures are the greatest,” Michalski said.
NOAA predicts that there’s a 60% chance of a return to neutral by March-April-May stretch.
“Based on the La Niña advisory, ‘La Niña conditions are present and are expected to persist through February and through April 2025,’ there’s a 59% chance of it persisting through that time period,” Michalski said.
This story was originally published January 10, 2025 at 11:59 AM.