Firefighters trying to curb massive wildfire in California's Yosemite National Park

Firefighters in California gained ground on Monday against a massive wildfire burning part of Yosemite National Park, although complete containment may be weeks away, officials said.

Crews working through the night got an edge on the so-called Rim Fire, a 350-square mile (906-square km) blaze that has charred the California park's Northwest, said Andrea Capps, spokeswoman for the Rim Fire command center.

They connected containment lines near the fire's northwestern and western borders, where most of the 4,500 homes threatened by the blaze are located, she said.

The fire was 60 percent contained by early Monday, a 15 percent increase from the night before.

"On Monday night is when it all really tied together," Capps said. "It's looking really good over there right now. They're calling that containment line secure."

Despite the jump in containment, Capps said fire analysts estimate that it could take until September 20 to contain the Rim Fire fully. Steep terrain and high, unpredictable winds will likely pose the main challenges in digging and burning containment lines around the blaze.

"The majority of the containment lines will probably be really strong by the middle, end of this week, but they just want to give themselves enough time to make sure it's fully contained," Capps said.

Wet weather expected in the area on Monday raised hopes, but the possibility of thunderstorms kept officials wary.

"Rain is good, but the winds that come with the pressure changes with the thunderstorms could lead to some unpredictable (fire) behaviour," Capps said. "We have had a few sprinkles on Tuesday morning, and so we're all waiting to see what happens."

While the majority of the fire was burning on Stanislaus National Forest, 60,214 acres, or about 27 percent, of the fire has crossed the Yosemite National Park border.

The massive blaze has scorched an area larger than many US cities and is the fourth-largest on record in California, burning more than 220,000 acres over the past two weeks.

Over the past several years, wildfires in the US West have become increasingly frequent and at times deadly. Earlier this year, 19 firefighters were killed in a blaze in Arizona, and wildfires have raged in several states, including Nevada, Alaska and New Mexico.