El Niño’s Return: What It Means for California’s Winter Weather

Climate scientists and weather forecasters suspect this winter could be as wet or wetter than last year’s torrential downpours. But just how wet will this winter become?

The answer isn’t quite as simple as forecasters pumping various inputs into computer models that then spit out what we can definitively expect. The Bay Area’s weather patterns are created by global patterns in the atmosphere, everything from interactions with the ocean, landscape and sun.

One of those natural factors is the climate pattern known as El Niño, which has returned after a four-year hiatus, ushering in the possibility of yet another stormy winter. This weather system has a 75%–85% chance of becoming a strong system from November to January, according to the National Oceanic and Atmospheric Administration.

What is El Niño?

El Niño — the opposite of La Niña, which recently ended a cycle — generally occurs every three to five years when ocean waters along the equator in the eastern Pacific warm by at least a half-degree Fahrenheit. That, in turn, can reposition the jet stream and funnel storms toward the West Coast of the U.S., often resulting in increased rainfall across thousands of miles.

Climate forecasters predict a range of strengths for the current El Niño — everything from a moderate to a super El Niño — which can often be characterized by intense warmer downpours.

“There is potential for a lot of strong storms with coastal issues, and we just do not have extensive flood systems on the coast of California,” said Gary Lippner, deputy director for flood management and dam safety with the California Department of Water Resources.

With winter just a few months away, climate and weather experts suggest preparing our homes and lives for the worst — major flooding. Keep reading for what to know about 2023’s El Niño, from its impact on California’s snow forecast to the timing of weather predictions.

Jump straight to:

• • What are the chances of a super El Niño?
  • Does a wet winter always mean snow in the forecast?
  • Is climate change intensifying El Niño?
  • How can I prepare my home for potential storms?

Is it possible to predict what winter 2023 will be like in California?

Kind of. It’s not possible to predict the day-to-day weather this far in advance. However, meteorologists are able to forecast possible climate changes that might happen.

“Right now, it is still too far out and our seasonal forecasting capabilities are very limited,” said Michael Anderson, California’s state climatologist.

There’s a 30% chance of a “historically strong” El Niño event, which could rival the ferocity of the 1997–98 years, according to NOAA’s latest El Niño Advisory, which saw flooding rains across the state. The scientists note that while a stronger El Niño can increase the likelihood of weather anomalies, it does “not necessarily equate to strong impacts locally.”

That’s because it’s usually only in the worst El Niño years that the entire state gets soaked — Southern California, on the other hand, has a slight tendency toward wetter conditions even in moderate El Niño years. (More on this below.)

Jan Null, a meteorologist with Golden Gate Weather Services, said the relationship between El Niño and Bay Area impacts is not always clear and that the best thing to do as a California resident is to prepare for the worst outcome.

“Climate models are showing this ambivalent pattern for California this winter,” he said.

As for a timeline, researchers think that peak impacts — big atmospheric rivers that drop a ton of rain — could arrive in the New Year through early spring.

“The closer we are to that winter rainy season forecast, obviously the better the prediction will be,” said John Chiang, a UC Berkeley climate scientist.

What are the chances of a super El Niño?

While most predictions of the intensity of El Niño range from moderate to strong this year, one forecasting group is predicting what they classify as a super El Niño on par with 1997–98. That winter saw a great deluge across the state, as rivers swelled, mudslides destroyed homes and roads filled with debris. At the end of it, 17 people had died and the state suffered nearly $1 billion in damage.

“It’s only been seen three times previously in the historical record,” said Stephen Yeager, project scientist with the National Center for Atmospheric Research. “We are looking at the potential of a major season-long event that could impact people and their livelihoods.”

For Yeager’s model, he and his team analyzed historical conditions from 1970 to 2019. They took atmospheric conditions into account — warmth, humidity and wind— as well as the state of oceans, ice and land. They then compared that historical data with computer model forecasts, which unveiled the potential for a super El Niño this winter.

“Our system is predicting a warmer event than many other [models],” Yeager said. “But it isn’t out of the realm of possibilities.”

Does a strong El Niño prediction mean a wet winter?

No, not all El Niños are the same. And even a strong system doesn’t mean California will get walloped by atmospheric rivers.

When looking at the historical record, Null said El Niño years have almost equally had above-average and below-average rainfall. For instance, the years of 2015–16 produced a very strong El Niño event but were relatively dry.

“Trying to say this is going to be a strong or very strong event doesn’t equate directly to ‘it’s going to be a wet year in California,’” he said.

He adds that an alphabet soup of other natural phenomena factor into the strength of El Niño and its potential effects, including the Madden-Julian Oscillation, the Pacific Decadal Oscillation and the North Atlantic Oscillation.

Does a wet winter always bring snow to California?

A wet winter does not always mean ample snow. Chiang, with UC Berkeley, said that El Niño tends to have warmer weather patterns, which can actually decrease snow amounts.

“That does play a role — but if you are high enough and cold enough, it will snow rather than rain,” he said.

Chiang adds that the effects of El Niño are not ubiquitous across the world, country or even one state. The climate system can mean wetter weather patterns in California and the Southwest and warmer weather in the Northwest.

At what point in the year do we begin to get firmer predictions for winter?

The only time we can really know what winter will be like is the moment that it ends, said Null, tongue in cheek.

Last year, the seasonal forecast for California’s winter was an even split for a wet or dry winter — and a few months later, torrential rain pounded the state for months.