Nov. 16 (Bloomberg) -- Hot, dry Santa Ana winds are driving wildfires across Southern California's Riverside and Orange counties today, the latest in a series that have burned 22,000 acres in the state and put 3,700 firefighters to work.

The winds, which blow from California's inland deserts over the mountains to the coastline and bring hot, dry weather, are responsible for the conditions, the National Oceanic and Atmospheric Administration said. September through November is the peak season for such weather.

``This is a pretty bad situation,'' said Michael Sager, a meteorologist at forecaster AccuWeather.com in State College, Pennsylvania. ``The heat and low humidity helps to pull moisture out of the plant life, so that it burns easier and burns hotter.''

The so-called Triangle complex of fires in the towns of Anaheim, Brea, Corona and Yorba Linda in Riverside and Orange counties have destroyed 64 buildings, including apartments and homes, said Daniel Berlant, a spokesman for the California Department of Forestry and Fire Protection.

Five thousand people have been evacuated and the fires threaten more than 3,500 homes. About 1,500 firefighters are battling the blaze as wind gusts of as much as 45 miles per hour (72 kilometers) complicate their efforts, Berlant said.

Sylmar, Montecito

Temperatures in Anaheim are expected to be as high as 92 degrees Fahrenheit (33 degrees Celsius) and 94 in Yorba Linda, the National Weather Service said. The winds will diminish as the week progresses because a high-pressure system is weakening as it moves east, said Carl Erickson, a meteorologist with AccuWeather. Temperatures will fall gradually into the upper 80s and humidity will increase, which should help curb the fires, he said.

The four cities are between 26 miles to 48 miles southeast of Los Angeles.

Governor Arnold Schwarzenegger has declared a state of emergency in Los Angeles, Riverside, Orange and Santa Barbara counties to free up state and federal funds to fight the fires, Berlant said.

A second fire, the Sayre fire near Sylmar in California's San Fernando Valley, has burned 9,500 acres and was about 30 percent contained, Los Angeles County Fire Department inspector Ron Haralson said. The blaze closed parts of Interstate 5, a main thoroughfare running the length of the U.S. West Coast from Mexico to Canada.

The fire department said more than $2 million has been spent fighting the fire.

The third fire is 92 miles northwest of Los Angeles in the town of Montecito, near San Barbara. It began Nov. 13 in the Los Padres National Forest and burned 1,940 acres. It was 75 percent contained after destroying 210 homes and damaging nine others.

To contact the reporter on this story: Dan Hart in Washington at dahart@bloomberg.net.

Last Updated: November 16, 2008 15:54 EST