A massive northern California wildfire that’s threatening Yosemite National Park and San Francisco’s key water and power sources grew Monday, becoming the 13th largest in state history, state fire authorities said.

The Rim Fire, which has devoured more than 149,000 acres, has scorched an area about the size of the city of Chicago while more than 3,600 firefighters try to rein it in. …

The wildfire, which was 15% contained Monday morning, was spreading primarily to east and threatened to grow amid extremely dry conditions and hot weather.

Part of the fire continued to spread Monday toward a key part of San Francisco’s water supply: the Hetch Hetchy Reservoir, which lies within Yosemite and is just east of the flames. …

A top priority is stopping the fire from spreading further in Yosemite National Park.