The large wildfire in the Angeles National Forest, just north of Los Angeles, threatens over 10,000 homes and the Mt. Wilson Observatory. The fire is burning in an area that hasn't seen a wildfire in 60 years. The severity of the fire is due to 10 years of drought and recent triple digit temperatures and low humidities.
Below is a satellite image of the southwest U.S., showing the large area of smoke from the fires (denoted in red). The image was taken on August 30 at 7:15 PM CDT. Click on the picture for a larger view.