Strengthening El Niño boosts odds of warmer Pacific Northwest winter

The third Thursday of the month has arrived, meaning the National Weather Service’s Climate Prediction Center (CPC) published its latest seasonal weather outlook for the nation. The fresh outlook again reflects the ongoing strengthening of El Niño as the winter season approaches.

The eastern Pacific tropical waters west of Peru have warmed to about 2.5 degrees Celsius or about 4 degrees Fahrenheit above average and are still climbing. This warming is the result of weaker-than-normal easterly trade winds across the Pacific.

El Niño sea surface temperature forecast guidance from around the globe indicates El Niño is expected to strengthen even more through the end of the year. In an El Niño Advisory statement from the CPC, there is a greater than 90% chance of a very strong event by the end of this year, and a near 70% chance this El Niño will be a record event, with records going back to 1950.

The just-released seasonal weather outlook reflects a strong El Niño episode through this winter. During El Niño, the Pacific storm track spends more time moving into California and across the southern tier of the nation. As a result, the Pacific Northwest usually has a warmer-than-average winter with no real trend on precipitation.

For the southern half of the country, the odds are strongly in favor of above-average and much-needed precipitation to help alleviate current drought conditions. For the Colorado River basin, the rise in precipitation and mountain snow should help start a rebound of much-needed water in the river. The other side of that coin, though, is a growing threat of too much rainfall at once, resulting in flooding and landslides.

For much of the Pacific Northwest, the three-month winter period of December through February shows a 60% to 70% chance of warmer-than-average temperatures — about as high as it’s ever been for such a seasonal weather outlook.

Impacts of El Niño

With Halloween approaching, the term El Niño often generates unpleasant scary implications. Yet in fact, of the three types of La Niña, Neutral, and El Niño conditions in the eastern Pacific tropical waters, El Niño tends to have less hazardous winter weather than La Niña and Neutral conditions in the Pacific Northwest.

La Niña is when those same eastern Pacific tropical waters are cooler than average, and Neutral is close to average. Both of these conditions also adjust how the North Pacific storm track behaves, spending more time moving into the Pacific Northwest versus California.

El Niño ranks last when it comes to hazardous fall and winter weather in the Pacific Northwest — flooding, strong damaging windstorms, and lowland snow and ice, as opposed to La Niña and Neutral. That does not mean these hazardous weather events do not occur. They just occur less frequently. In fact, of Seattle’s top 10 snowiest winters, three of them have been during El Niño winter seasons while the rest have been La Niña seasons.

Yet a big impact of El Niño and its warmer-than-average conditions implies another below-average mountain winter snowpack, not good news for skiers and water managers. Another subpar mountain snowpack would make that 5 years in a row, leaving more limited water supplies for agriculture, fish, electric power generation, and drinking water, and the likelihood of another active wildfire season with more smoke and air quality issues next year.

Heading well into next year, this El Niño episode is likely to wane, yet is anticipated to leave an El Niño hangover. The temperature outlook all the way through to near the end of 2027 shows ongoing chances of warmer-than-average temperatures, another reason for concern about next year’s wildfire season.

What you can do

Regardless, now is the time to prepare in advance for whatever hazardous fall and winter weather lies ahead. Visit ready.gov, the Washington State Emergency Management Preparedness webpage, or your local county or city emergency management websites for helpful readiness information for your home, car, business, and pets.

Again, preparing ahead of time before a significant storm arrives or a big earthquake occurs is a good time to get ready, particularly while needed supplies are readily on hand from retailers.

Ted Buehner is the KIRO Newsradio meteorologist. Follow him on X and Bluesky. Read more of his stories here.