Feb 21, 2024 - News

What the new La Niña watch means for Washington

Probability of El Niño or La Niña
Data: NOAA; Chart: Erin Davis/Axios Visuals

The strong El Niño pattern that was predicted to usher in some of the Pacific Northwest's hottest temperatures ever this summer is fading, with climatologists watching for signs of the cooler La Niña phase.

Why it matters: The onset of La Niña could suppress global temperatures, potentially preventing the record-breaking heat forecast for 2024.

Driving the news: The National Oceanic and Atmospheric Administration issued a La Niña watch earlier this month, indicating that the current strong El Niño may be ending this summer, with a 77% chance of a La Niña developing by fall.

What's happening: While the shift may seem abrupt, there's a historical pattern of La Niña events following strong El Niño episodes, said Michelle L'Heureux, a physical scientist at NOAA's Climate Prediction Center.

  • Coming off the peak of tropical Pacific overheating can bring a certain degree of momentum that's sometimes "strong enough that you shoot into a La Niña," L'Heureux said.

Zoom in: Warm and dry are still the watchwords for Washington and Oregon this summer, as the influence of La Niña is not expected to hit until around September, interim Washington state climatologist Karin Bumbaco told Axios.

Yes, but: A La Niña winter at the end of 2024 is potentially very good news for Washington's snowpack, which determines water supply and is arguably the most crucial climate-related variable in the Pacific Northwest, Bumbaco said.

  • Snowpack in the Olympic Mountains is currently around 32% of median values, 50% in the North Cascades and 60–75% in the Southern Cascades, per Bumbaco.

Catch up quick: El Niños generally bring drier, warmer, less snowy winter conditions to Washington and Oregon and wetter conditions, including extensive rain and flooding, to the southern two-thirds of California.

The big picture: Added to human-caused global warming, heat from El Niño's above-average sea surface temperatures helped make 2023 the hottest year on record.

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