Rising temperatures pose new challenges for firefighters who have made incremental progress against a massive wildfire in central California that has injured four people as it has become the biggest blaze in the state so far this year.

The Gifford Fire burning through the rugged backcountry of California's Central Coast is now the state's largest wildfire of the year. It has reached so-called "mega-fire" status and is one of 38 large fires burning across nine states.

The Canyon Fire, which began on Thursday afternoon, has blazed through nearly 5,000 acres in less than 24 hours.

New evacuations have been ordered in Central California as the massive Gifford Fire nears 100,000 acres burned.

Two wildfires caused by lightning strikes were burning out of control in northwest Colorado on Sunday, forcing evacuations that included nearly 200 inmates at a nearby prison. NBC News’ Dana Griffin has more.