West Coast watches for La Niña
Add Axios as your preferred source to
see more of our stories on Google.
A developing La Niña could mean big weather shifts for the West Coast this winter, including colder, wetter conditions up north and drier, warmer weather farther south.
Why it matters: From Seattle to San Diego, La Niña helps steer the storm track, shaping water supplies, snowpack and drought risk.
Driving the news: NOAA scientists say there's a better-than-even chance that La Niña will develop this fall and winter, with current outlooks showing just over a 50% chance by September to November and probabilities increasing into winter.
- A La Niña Watch means "conditions are favorable" for La Niña to form within six months, Michelle L'Heureux, meteorologist and El Niño–Southern Oscillation team lead at NOAA's Climate Prediction Center, tells Axios.
- But she cautions it's not guaranteed.
How it works: La Niña occurs when sea surface temperatures in the central and eastern Pacific Ocean are cooler than average, according to NOAA.
- That cooling nudges the jet stream north and, because it acts like a fast-moving conveyor belt of air, tends to carry storms into the Pacific Northwest and northern U.S. while leaving the South drier.
- San Francisco, perched on the boundary, is a "wild card" and can go either way, says Johnna Infanti, another NOAA meteorologist.
Threat level: NOAA says a weak La Niña may not bring "conventional impacts," but its influence can still shape seasonal outlooks — so even subtle ocean changes are worth watching.
The intrigue: While most of the world's oceans are warming, the eastern tropical Pacific is not — a twist that sharpens the temperature contrast central to La Niña, climate scientist Daniel Swain tells Axios.
- Models once predicted the east would warm faster, favoring more El Niños, but instead La Niñas have become more frequent.
- It suggests the models are off or we're in a human-driven transition, said Swain.
- With a "La Niña-like" ocean background, even modest events can "punch above their weight," he said.
What's next: NOAA updates its outlooks monthly and will issue a La Niña advisory if temperatures in the tropical Pacific fall at least 0.5°C (0.9 °F) below average and the atmosphere shows consistent signs of the pattern.