Hopes for a wet winter and spring for drought-parched California grew Thursday as researchers predicted that there’s at least a 95 percent chance of a historic El Niño on the way.

But the precipitation likely won’t come in time to bail the state out of its fourth year of crippling drought, or provide relief to California’s destructive fire season, according to a monthly climate report from the National Oceanic and Atmospheric Administration.

“There is a greater than a 95 percent chance that El Niño will last through the wintertime, and there is good confidence it will last into the spring,” said Dan Collins, a research scientist with NOAA’s Climate Prediction Center.

The stronger the El Niño, the more rain, history shows, and eastern Pacific Ocean temperatures have reached the warmest weekly average since the 1997-98 El Niño — the strongest event in modern history.

Collins said there is a very high probability that this year will be hotter and have more rain than average, but those weather patterns likely won’t start impacting Central and Northern California until December.

Another NOAA report released last week warned California communities about record floods due to rising sea levels and El Niño.

In the meantime, last month was the warmest August on record, and there is a 97 percent chance that, globally, this year will be the hottest ever, said NOAA climate scientist Deke Arndt.

The monthly forecast for October shows higher-than-average temperatures that will persist along the entire West Coast through December. El Niño-driven rain won’t begin affecting the central and northern parts of California, where a four-year drought continues to intensify, until the end of the year, scientists said.

The drought, which has annihilated the state’s snowpack in the High Sierra to the worst in 500 years and turned the landscape into a tinderbox for wildfire, will get stronger through the end of the year, scientists said.

Destructive wildfires have ravaged the state this fire season. The Valley Fire, which continued to burn Thursday, has destroyed at least 585 homes and charred 73,700 acres in the communities around Middletown in Lake County.

In the Sierra foothills, the Butte Fire has burned 252 homes over the past week.

The Valley Fire and the Butte Fire are the ninth- and 14th-most destructive in the state’s history. Those rankings could rise as surveyors get into the burn areas and more closely assess the damage.

Evan Sernoffsky is a San Francisco Chronicle staff writer. E-mail: esernoffsky@sfchroniclc.com Twitter: @EvanSernoffsky