With wildfires raging and three months to go before the start of the winter rainy season, drought-stricken California received promising news Thursday: El Niño conditions in the Pacific Ocean continue to gain momentum, increasing with every week the chances of desperately needed wet winter weather on the West Coast.

“We are predicting this El Niño could be among the strongest El Niños in the historical record dating back to 1950,” said Mike Halpert, deputy director of the National Oceanic and Atmospheric Administration’s Climate Prediction Center in College Park, Maryland.

The surface temperature of Pacific Ocean waters along the equator off Peru is now 3.42 degrees Fahrenheit warmer than the historic average, the highest reading ever recorded in early August. And significant winds continue to blow from the west, pushing the warm water toward North America and South America — both classic signals of a strong El Niño.

But drought-weary Californians may not want to bet the rent just yet that they’ll be watering lush green lawns next summer.

Even though California has historically seen wet winters during strong El Niño events like the one now underway, experts say, there are at least four or five major scenarios in which this El Niño could fail to end the state’s drought.

“It’s very unlikely that things will develop exactly as we’re hoping for,” said Jay Lund, director of the UC Davis Center for Watershed Sciences. “In some areas, the drought might be over, and in some areas it might be worse than others.”

What could go wrong?

First, big storms could develop, but mostly hit Southern California, missing Northern California. Last month, San Diego and Los Angeles broke records for the wettest July ever, and a highway bridge washed out in a flash flood on Interstate 10 east of Palm Springs, while the Bay Area remained mostly sunny. The disparity is a problem for California’s water supply, because many of the state’s most important reservoirs are in the north, from Shasta to Oroville to Folsom. To fill up, they need lots of water.

“If we get a lot of rain, but it doesn’t get north of Interstate 80, it won’t put as big a dent in the drought,” said Jan Null, a Saratoga meteorologist.

A second pitfall could come if big El Niño storms arrive, but they are too warm to deliver a large Sierra snowpack, or if record warm temperatures like California experienced last spring melt what mountain snow does arrive.

The Sierra snowpack is a giant bank of water in good years, holding roughly a third of the state’s water supply, then releasing it during the spring and summer months as it melts. Torrential warm winter storms will help fill dams, but much of the water could run off to the ocean, particularly if dams are nearing full capacity at the time. And those kinds of storms are more likely to cause flooding and mudslides.

“We want the snowpack for sure,” said California’s state hydrologist, Maurice Roos. “The water comes off in a much more controlled fashion. It does more good to come off gradually. It feeds the mountain streams, it has a longer duration of flow, which is good for fisheries, and it helps recharge the groundwater.”

Another risk: Nobody really knows what will happen if El Niño storms hit the “Ridiculously Resilient Ridge.” That’s the giant mass of dense high pressure off the West Coast that has blocked other storms from drenching California in recent years, largely causing the historic four-year drought. Scientists also don’t know how “the blob,” a huge mass of record-warm ocean water now stretching from California to the Pacific Northwest, might affect storms.

Null said he thinks the subtropical jet stream, which moves huge amounts of moisture to California during strong El Niño winters, could slip under the ridge. Other scientists say the two may battle, like monsters in a 1950s Godzilla movie.

“It certainly is a wild card,” said Null. “It might not be a significant factor but nobody really knows.”

Finally, there is simply bad luck.

“The correlations between precipitation and El Niño are far from perfect,” said Kevin Werner, NOAA’s director of western region climate services. “There are examples from the recent past when El Niño events were drier than average.”

Since 1951, there have been five winters with strong El Niño conditions, meaning ocean water at the equator that is significantly warmer than normal. In four of those winters — 1957-58, 1972-73, 1982-83 and 1997-98 — rainfall in the Bay Area and Los Angeles was at least 140 percent of the historic average, according to studies by Null, a former National Weather Service forecaster.

But in 1965-66, the strong El Niño didn’t deliver above average rain. It simply fizzled out.

However, Thursday’s news, in the monthly El Niño report from NOAA and Columbia University, boosted hopes of drought-weary Californians.

The system that is emerging is so potentially powerful that one NOAA research scientist has nicknamed this year’s El Niño “Bruce Lee,” after the lightning-fisted Chinese martial arts star.

The last time there were similar conditions, in the winter of 1997-98, downpours filled California reservoirs, Bay Area cities received double their average rainfall, the Sierra was dumped with snow and rivers rushed to flood stages.

There is now a 95 percent probability of El Niño being present through the end of 2015, and an 85 percent probability it will continue into 2016, according to the report.

Still, experts noted Thursday that California has suffered very large rain and snow deficits over the past four years, and needs 150 percent or more of normal rainfall statewide this year to make a major dent in the drought. So even in a soaking winter, those deficits are not likely to be erased in one year, although they would help a great deal.

“It would be an interesting dichotomy,” NOAA’s Halpert said, “to have flooding while you are still in the midst of a severe drought.”

Paul Rogers covers resources and environmental issues. Contact him at 408-920-5045. Follow him at Twitter.com/PaulRogersSJMN