The El Niño brewing in the equatorial Pacific is on course to become one of the strongest — if not the strongest — such system on record, the Climate Prediction Center announced Thursday.

What that means for drought-stricken California is not yet determined, but the odds increasingly favor a wet winter for at least the southern half of the state.

Climate experts declare an El Niño when the sea-surface temperatures in a key region of the central Pacific are at least 0.5 of a degree Celsius (0.9 Fahrenheit) above normal for several months. The warm waters add energy and moisture to the atmosphere, and in combination with changes in wind and air-pressure patterns, can alter the storm track over North America and much of the globe.

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But only the strong El Niño episodes, when those waters have been a minimum of 1.5 degrees Celsius above normal, have been reliable providers of ample rainfall in California. The system building up this year has the potential to blast past the two previous giant episodes — in 1982-83 (2.1 degrees Celsius above normal) and 1997-98 (2.3 degrees Celsius higher).

“Peak anomalies in the Pacific could approach or even exceed 2 degrees Celsius,” said Mike Halpert, deputy director of the Climate Prediction Center in College Park, Md. “It looks like it will be one of the three or four strongest events on record. Whether it matters if it’s 1, 2, 3 or 4 is debatable.”

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Some climate models show that anomalies in the equatorial Pacific’s surface temperatures will rise above 3 degrees Celsius during the coming winter. If that plays out, it would be an unprecedented phenomenon.

Halpert cautioned that predicting the rise of sea temperatures is not the same as forecasting the impacts of a big El Niño.

Climatologists know what happened in 1982-83 and 1997-98: California got pounded by a series of powerful storms. Coastal zones suffered severe erosion, inland areas became flooded, homes were destroyed and agricultural losses mounted. In 1982-83, damage related to El Niño topped $1 billion in the state. Flooding in Gulf Coast states caused $1.2 billion in damage.

Climate experts, including Halpert, recognize that the two previous giant El Niños on record represent a small sample size. Climate models also factor in other atmospheric conditions present around the globe, and those could temper or amplify El Niño’s role.

Conditions this year — especially a large, warm pool of water in the North Pacific — are different from what was present in the ’80s and ’90s.

Early this week, the Climate Prediction Center’s models showed that Southern California is likely to be wet this winter. Much of Northern California also stands a good chance for a wetter-than-normal winter, but the likelihood is not as great as in the southern end of the state.

Water regulators in Sacramento and local water managers, who have all been stressing water-saving measures for residents and businesses after mandated cutbacks from Gov. Jerry Brown, are cautiously optimistic that El Niño will deliver. But they aren’t counting on it to bail out the state, especially in the long term.

“It’s an interesting dynamic,” said Felicia Marcus, chair of the State Water Resources Control Board. “We want as much rain and snow as possible that doesn’t flood people, and the odds seem to be good. But with the drought , it’s not over until it’s over.”

Marcus used another Yogi Berra quote to illustrate the uncertainty of the forecast: “It’s difficult to make predictions, especially about the future.”

The question of where and how the precipitation falls is also critical for drought relief, Marcus said. Last year, the state lost nearly a third of its water supply when very little snow fell in key regions of the Sierra. Snowmelt feeds the state’s major reservoirs in the north.

“It will take a lot for us to get out of the drought,” Marcus said. “It could take more than a year. This is not the typical drought that we’ve seen before. This is the drought of our lives, and our parents’ lives and our grandparents’ lives.”

Dana Friehauf, water resources manager for the San Diego County Water Authority, said it will be extremely important for people to continue their conservation efforts.

“While one wet year will definitely help, we could go right back into another drought,” Friehauf said. “Water that is conserved now can be kept in storage, and we’ll be better prepared for the next drought.”

Beyond California, El Niños can have effects worldwide. They tend to tamp down hurricanes in the Atlantic, which has been quiet so far this year, and pump up hurricanes in the eastern Pacific, which has been highly active in 2015.

Floods often occur along the west coast of South America during El Niño years, while droughts are common in Australia and Indonesia. The 1982-83 El Niño caused an estimated $8.1 billion in damage worldwide.