46 large fires burn across 8 states as heat wave grips U.S. West

• "Heat-related warnings, and advisories extend across most of California and Nevada into the interior Northwest," the NWS said.
• New large blazes ignited in California, Montana, Oregon, Washington and Wyoming on Wednesday, as firefighters face "hot and dry conditions," per the National Interagency Fire Center, the nation's support center for wildland firefighting.

By the numbers: More than 10,200 firefighters and support personnel are responding to wildfires across the U.S. — with 46 large fires now burning, according to the NIFC.

• 14 of these are in Idaho, 10 in Montana, nine in Oregon, six in California and four are in Washington state. Utah, Arizona and Wyoming each have one large fire burning, per the NIFC.

The big picture: There are concerns more fires could ignite in California, where triple-digit temperatures are forecast — and where the grid operator has issued a statewide "flex alert" call for voluntary energy conservation for Friday, marking the third straight day it's done so.

• One of the biggest blazes Californian firefighters are battling in the state are the Route Fire, near Castaic, which ignited Wednesday and saw residents in Los Angeles County briefly evacuated. It's burned more than 5,200 acres and was 27% contained on Thursday night, according to Cal Fire.

• In San Diego County, the Border 32 Fire that also ignited Wednesday has razed over 4,400 acres and was 14% contained.

Meanwhile, a wildfire near the Oregon-Idaho border shut Interstate 84 in both directions on Thursday afternoon, AP reports.

Context: Climate change is escalating the threat of heat waves, wildfires and other extreme weather events, per Axios' Andrew Freedman.

Go deeper... Study: Climate change main cause of wildfire weather in U.S. West