Thousands forced to flee tiny, Gold Rush-era towns in California

A scorched car rests next to a residence levelled by the Detwiler fire near Mariposa, California. Photo / AP

Melted lawn chairs rest outside a residence. Photo / AP

A surging bushfire has raced through Californian mountains and foothills west of Yosemite National Park, forcing thousands to flee tiny, Gold Rush-era towns and wafting a smoky haze over the park's landmark Half Dome rock face.

The four-day-old blaze nearly doubled in size from about 100 sq km to more than 180 sq km today.

Yosemite, where campgrounds are open for the busy northern summer season, does not appear at risk from the fire, which is moving south, away from the park, authorities say.

The blaze has forced more than 4000 people from homes in and around half-a-dozen small communities.

Heavy smoke hung in the air over Mariposa, a town of 2000 with century-old wooden buildings.

Record rain and snowfall in the mountains in winter abruptly ended California's five-year drought but that has increased the challenge for crews battling flames feeding on dense vegetation.

Statewide, about 6000 firefighters were battling 17 large bushfires, including about 2200 at the fire near Yosemite. In Nevada, firefighters have a handle on a wind-driven wildfire that destroyed four homes and damaged several more.

Meanwhile, British Columbia's Government has taken the unprecedented step of extending a state of emergency by two weeks as it battles 140 bushfires that have forced about 45,000 people from their homes.

"Traditionally when an emergency is declared people are usually back in their homes within the two-week period. That may not be the case for many individuals," the Canadian province's Premier, John Horgan, said.

On July 7, the Canadian province declared its first state of emergency since 2003 as gusty winds fanned fires that were caused by lightning and humans in the tinder-dry central and southern regions.

Canadian military aircraft have joined thousands of firefighters from as far away as Australia to battle the fires. Today, 140 fires were raging in the province, down from 163 on Monday due to cooler, less windy conditions. About 353,000ha has been burnt since the beginning of the fire season in April.

- AAP