Over 12,000 people in eight California counties are under wildfire evacuation evacuation orders — most impacted by America's biggest blaze, the Dixie Fire.

Threat level: The Dixie Fire, the second-largest in Californian history, has razed more than 482,000 acres and was 22% contained, as it flared up in Lassen County late Monday. Smoke from 108 large fires in the West has reduced air quality in the eastern U.S. this week, with places including New York City, Iowa and Minnesota experiencing hazy skies.

• Air quality in Denver has been particularly bad, with smoke California's 11 large fires traveling some 1,000 miles as the Colorado city records some of the worst air quality in the world.
• Firefighters across the West also now face the threat of another extreme heat wave this week.

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

For the record: The Dixie Fire has now destroyed 873 buildings and Cal Fire doesn't expect it to be contained until Aug. 30.

• Heavy smoke from the blaze abated earlier Monday, enabling firefighting aircraft to help joint the containment fight, AP notes.
• By Monday night, the wildfire was raging along the Moonlight fire burn scar, near Westwood in Lassen County, according to Cal Fire and images taken from the scene.
• Plumas County Sheriff's Office officials said at a Monday evening briefing that four people listed as missing had been accounted for.