The improved outlook comes after weeks of frustration in snuffing out the crisis, as crews contended with water shortages, gale-force winds, bone-dry air, and a steady outbreak of new fires that have stretched resources thin.
The fresh optimism coincides with a planned visit by President Donald Trump later on Friday to survey the destruction.
Water shortages, gale-force winds, bone-dry air and new outbreaks have stretched resources thin. (EPA PHOTO)
Trump has sharply criticised local and state officials for their handling of the massive fires, which have incinerated entire neighbourhoods, killing 28 people and damaging or destroying nearly 16,000 structures.
As much as 1.5 inches of rain was expected to fall this weekend as hot, dry Santa Ana winds eased, said Rich Otto, a meteorologist with the National Weather Service's Weather Prediction Center.
After gusts of nearly 100 km/h on Thursday, winds would top out at 40 to 65 km/h on Friday and diminish through the day.
"It'll be a cold rain starting late Saturday and continuing into Monday, with some snow in higher elevations, but the concern is areas with burn scars from the fires," he said.
But the region's first significant rainfall in months would also increase the risk of dangerous mudslides on hillsides denuded of vegetation by fires over the past two weeks.
Red flag warnings, signaling extreme fire danger, are set to expire in the Southern California area at 10am local time, said Andrew Orrison, a meteorologist with the National Weather Service.
"Basically, the reason is because of the slackening winds," he said.
The Eaton fire destroyed much of the Altadena community near Pasadena. (EPA PHOTO)
"The changing conditions will also bring higher humidity which should help fire containment."
The latest big fire to break out in the Los Angeles area has already scorched more than 4,100 hectares in the San Fernando Valley but firefighters managed to achieve 36 per cent control of the Hughes Fire's perimeter by late Thursday, the California Department of Forestry and Fire Protection said on its website.
The Eaton and Palisades fires - on the eastern and western flanks of the metropolis - have burned for 18 days.
The Eaton Fire, which destroyed much of the Altadena community near Pasadena, was 95 per cent contained, raising hope that firefighters could encircle its entirety on Friday.
The Palisades Fire, which has devastated the affluent Pacific Palisades enclave near Santa Monica, was 72 per cent contained, Cal Fire said, late on Thursday.
A series of smaller fires also menaced the area in recent days. The Sepulveda Fire, which began early Thursday morning, has burned 18 hectares along the 405 freeway near the Getty Center museum - home to numerous art treasures. Now 60 per cent contained, the fore briefly caused part of the busy highway to be closed and forced some evacuations.
Two new blazes erupted on Thursday in the San Diego area. Evacuation orders were ordered but later lifted on Thursday in the La Jolla enclave near the University of California, San Diego, School of Medicine, after a two-acre brush fire erupted.
A second fire, further south near the US-Mexico border, spread through the Otay Mountain Wilderness, and was reported at 1700 hectares and zero per cent contained late on Thursday.
