William Brangham:

Once again, thousands of California firefighters are battling fast-moving blazes across the state. Driven by strong winds and dry conditions, the fires are forcing tens of thousands to evacuate their homes.

Hundreds of schools were closed due to poor air quality and closed highways. The Kincade Fire, in Northern California's Sonoma County, doubled in size in less than 24 hours. It's already destroyed at least 49 structures and burned more than 21,000 acres. It's just 5 percent contained.