FALLBROOK — A wildfire on the Camp Pendleton Marine Corps base in northern San Diego County triggered evacuation orders early Thursday as Santa Ana winds brought dangerously gusty and dry conditions to Southern California.

Evacuation orders were issued for about 7,000 residents on the west side of the community of Fallbrook and for some Camp Pendleton locations, the base and the California Department of Forestry and Fire Protection said.

The fire was estimated at 4.7 square miles around dawn, the Marine Corps said.

Cal Fire said firefighting aircraft were en route.

The National Weather Service forecast moderate to locally strong Santa Ana winds Wednesday through midday Thursday.

The San Diego weather office reported that the winds had peaked and were slowly weakening. The highest windspeed recorded in San Diego County was 71 mph.

Utilities proactively cut power to thousands of customers in targeted areas to prevent fires from being ignited by downed lines or sparks from wind-blown debris striking electrical equipment.

As of early Thursday, Southern California Edison had shut power off to more than 18,000 customers and was considering cuts to 155,000 others. Almost 6,800 San Diego Gas & Electric customers were blacked out and more than 24,000 others were warned they also might lose power.

Camp Pendleton sprawls over 195 square miles of coastal and mountain terrain.