Fresh evacuation orders were issued in California and Montana Wednesday, as firefighters in U.S. western states battled 105 large fires — and authorities warned more wildfires could ignite as a dangerous heat wave looms.

Driving the news: The National Interagency Fire Center said Wednesday fire managers could see an "[i]nitial attack and large fire activity could increase in the Northern California, Northwest, portions of the Great Basin and Northern Rockies areas due to hot, dry, and windy conditions and the potential for lightning."

Of note: California's historic Dixie Fire that's destroyed over 1,000 buildings and razed more than 505,000 acres was raging at 30% containment overnight.

• Elsewhere in Northern California, the Yuba County Sheriff's Department issued evacuation orders for several communities after the Glen Fire ignited and rapidly spread on Wednesday.
• The fire had burned 275 acres and was threatening an area south of Brownsville at 10% containment Wednesday. Evacuation orders were later lifted for some towns.
• In Montana, evacuation orders were issued over the Richard Spring Fire, burning south of Colstrip across the Northern Cheyenne reservation.
• The wind-driven blaze that's threatening "multiple communities" has destroyed nearly 150,000 acres and was 15% contained on Wednesday, according to Inciweb.

The big picture: 25 large wildfires were raging in Montana — more than any other state. Red flag warnings had been issued for most of the state Wednesday. Northern California was also under red flag warnings, as 11 large fires burned across the state.

• Red flag warnings were also in effect in Oregon, where 16 large fires were burning, and Washington state, where 15 big blazes were raging.
• Wildfire smoke was continuing to "plague parts of the West Coast, the Intermountain West, and High Plains with poor air quality through Wednesday," the National Weather Service said.

Context: A sweeping new report from the UN's IPCC concludes: "Human influence on the climate system is now an established fact."