An unusually strong Santa Ana storm moved across San Diego County late Monday and was expected to strengthen sharply Tuesday, potentially sparking wildfires, snapping trees and ripping apart Christmas decorations from the mountains to the sea.

In a rare move, San Diego Gas & Electric notified more than 117,000 customers over the weekend that the company may temporarily shut off power to reduce the risk of wildfires and that the outages could last a day or longer.

On this warning Monday, the campaign was implemented for tens of thousands. As of 6:15 p.m. Monday, the lines of more than 29,000 customers in 11 East County and hinterland areas, including Alpine, Valley Center, Boulevard, Campo, Descanso, Julian and Jamul, were “off.”

And that number was expected to have increased significantly by dawn Tuesday.

“The winter rains just haven’t shown up and we’re seeing some very critical fire weather conditions coming up this year,” said Brian D’Agostino, vice president of wildfire and climate science at SDG&E.

The potential for damage is also high as the winds are unusually strong and the relative humidity is very low. Wind gusts of up to 70 mph may occur in the mountains, 50 to 60 mph on portions of Interstates 8 and 15, up to 40 mph on State Route 76 and up to 30 mph along the coast.

Forecasters said the winds would be noticeable in East County around midnight and begin whipping some coastal areas by sunrise.

Some of the strongest gusts are expected to follow a corridor from the Ramona and Escondido areas to Encinitas and Del Mar. Winds will also sweep over Camp Pendleton and along a stretch of Interstate 8 east of Alpine known for its high winds. associated traffic accidents.

The potential for large-scale fires has not been this high since the first week of December 2020, when fires broke out in many parts of the county.

“The highest risk areas for this particular event … will develop in areas above 3,000 feet,” D’Agostino told reporters Monday morning, adding that gusts are expected to blow through much of rural and chaparral-covered backcountry areas, one of the most flammable vegetation types in the country.

“As we head up Boulder Creek Road toward the western slopes of Cuyamaca, we believe winds there could easily reach hurricane force from this event,” D’Agostino said.

SDG&E expects to implement public safety power shutoffs, de-energizing power lines as a precautionary measure to reduce the risk that strong winds could knock them into dry vegetation and spark a wildfire.