La Niña Is Back: Puget Sound Poised For A Cooler, Wetter Winter

SEATTLE — Prospects for another robust winter are improving in Western Washington, as La Niña conditions officially emerge for the second year in a row. The weather phenomenon occurs when the water near the equator of the Pacific Ocean is cooler than average. In North America, its effects on the climate are most pronounced in the winter months.

Strong La Niña winters typically bring colder, wetter, snowier weather to the Pacific Northwest and other northern states, while the South tends to see warmer and drier conditions. Last winter, the phenomenon lent a hand in bringing Seattle one of its snowiest days on record and helped build up a healthy snowpack in the mountains.

Climatologists at the National Oceanic and Atmospheric Administration started spreading the word for a potential "double-dip" La Niña back in July, and forecasts since have only strengthened. On Thursday, NOAA's Climate Prediction Center confirmed La Niña's highly-anticipated arrival and predicted it would last into next spring.

Having consecutive La Niña winters is far from uncommon, and NOAA notes the phenomenon has earned "frequent-flier" status recently, having been present in 2016, 2017, 2020, and now, 2021.

"Our scientists have been tracking the potential development of a La Niña since this summer, and it was a factor in the above-normal hurricane season forecast, which we have seen unfold," said Mike Halpert, the center's deputy director. "La Niña also influences weather across the country during the winter, and it will influence our upcoming temperature and precipitation outlooks."

While no two La Niñas are exactly the same, they do share a few things in common.

NOAA explains:

"We’ve already seen one likely effect of La Niña this year—a more active Atlantic hurricane season, with nearly twice as many storms as average so far this year. But the most substantial La Niña effect on North American rain, snow, and temperature happens during winter. In summary, La Niña winters tend to be drier and warmer across the southern third of the U.S., and cooler in the northern U.S. and Canada. The Pacific Northwest, the Tennessee/Ohio Valleys, and parts of the Midwest tend to see more rain and snow than average."

One big variable for La Niña winters is how much they impact snowfall. Current projections call for a weaker pattern this year, which could limit some of the snowier effects Puget Sound saw last winter in the lowlands. However, even weaker years tend to see above-average snowfall in the mountains, which is good news for skiers and our water supply.

Here is a look at the differences in snowfall patterns during weak and strong La Niña years:

Regardless of what kind of precipitation falls, the models are in agreement that Puget Sound is looking at a soggy season ahead. The latest seasonal outlooks paint the same picture, projecting above-average moisture in Washington clear through February. There could be good news for snow, too, with temperatures expected to trend below normal by December.

If the uncertainty is too much to bear, fear not: NOAA will share its official winter predictions on Oct. 21, providing a final, comprehensive overview of what forecasters expect for the colder months.

Learn more about La Niña's arrival on NOAA's Climate Blog.