Update 10/25/07: Conditions are improving as the Santa Ana winds abate. See this NPR report for more.

Once again the hills of southern California are ablaze with over a dozen wildfires whipped up by strong Santa Ana winds . As of this writing, the fires are burning out of control threatening thousands of homes as the advancing fire front marches toward the ocean. Thousands of residents are being evacuated.

Rapid Growth of Wildfires 10/22/07
Courtesy NASA

Santa Ana winds are a common feature of the dry summer subtropical climate of southern California. The typically dry summer conditions has been made worse from a prolonged period of below normal precipitation.

Wind speeds have been reaching upwards of 70 mph hour, with gusts to hurricane force levels. Air temperatures can reach 100 F. The fires are expected to burn for the next few days as the warm winds continue to stream across Southern California.

Santa Ana conditions. Courtesy NASA.