LOS ANGELES, July 4 (Xinhua) -- A wildfire in central California had rapidly grown to more than 70,000 acres (283.2 square km) in around 48 hours by Friday noon, becoming the largest blaze so far this year in the western U.S. state.

The fire, dubbed the Madre Fire, started Wednesday afternoon in San Luis Obispo County, according to the California Department of Forestry and Fire Protection (Cal Fire). It was only 10 percent contained.

Authorities said fire behavior in the area is expected to be extreme, characterized by rapid uphill runs and wind-driven head fire spread.

"The presence of dry, cured annual grasses will support high rates of spread with intense flame lengths. Alignment of slope and wind will further exacerbate fire behavior, creating challenging suppression conditions," incident commanders noted in an update.

More than 600 firefighters are battling the fire and at least 50 structures are threatened by the blaze.

Across California, spring 2025 was warmer and drier than normal, Cal Fire said in a seasonal outlook on its official website, adding that fire potential in the state is expected to increase steadily through the summer. ■