Wildfires ravage communities in Northern California as thousands evacuate

• Mandatory evacuation orders were in effect for both fires.
• Threat level: Firefighters were facing the threat of extremely dry forests combined with Red Flag fire weather conditions overnight.

By the numbers: As of Wednesday evening, the River Fire had burned 1,400 acres and was 0% contained.

• The Dixie Fire is now the 8th-largest blaze in California history by acres burned, at more than 274,000 acres so far.
• Context: Several, but not all, of the fires in northern California have been burning for some time.
• Illustrating the dangerous conditions in place, the River Fire exploded from a spark on Wednesday to well over 2,000 acres by dusk and growing quickly, threatening several small towns, and billowing smoke more than 30,000 feet into the sky.

Our thought bubble: The extremely dry conditions in northern California are the result of a severe drought, which is the worst the West has seen so far this century.

• Northern California as well as the neighboring states of Oregon and Washington have also experienced repetitive heat waves this summer that have dried out the forests even more, and shrunk lakes and reservoirs to record low levels.

• Human-caused climate change is driving an increase in the likelihood and severity of heat waves and droughts, and is behind a trend toward larger wildfires in much of the West in recent years, studies show.
• Last year was California's worst wildfire season on record. So far, this season is ahead of last year's pace, and the climatological peak of the season doesn't begin for several more weeks.