The number of San Diego Gas & Electric customers in backcountry communities without electricity because of power safety shutoffs grew after blustery Santa Ana winds blew through San Diego County overnight. As of 9 a.m. Thursday, 1,263 customers had their electricity pre-emptively cut off in the hopes of reducing the risk of wind knocking power lines to the ground and potentially igniting a wildfire. On Wednesday, the number of customers without power stood at about 700. SDG&E officials estimated that power will be restored by 5 p.m. Friday. Planned outages known as Public Safety Power Shutoffs were implemented after the National Weather Service earlier this week issued red flag warnings, alerting people throughout San Diego County of gusty winds and dry conditions. The red flag warnings remain in effect through 11 a.m. Friday. The power shutoff impacted the Mountain Empire Unified School District, which closed its schools Thursday for a second straight day. The rural East County district cited high winds and the danger it posed for high-profile vehicles like school buses when they canceled classes Wednesday. Power was cut Wednesday to 341 SDG&E customers in Potrero, 187 customers in Alpine, 18 in Descanso, 18 in the Buckman Springs area and 16 in Jamul. Earlier in the day, electricity was turned off to customers in other East County communities such as Campo, Boulevard, Jacumba and Live Oak Springs. SDG&E reported gusts as high as 66 mph at 9:50 p.m. Wednesday at Sill Hill near Descanso. Windy conditions persisted Thursday morning, with the utility’s weather center recording gusts of 41 mph at Hauser Mountain, 38 mph at Lucky 5 Ranch in Anza-Borrego and 34 mph at East Willows Road, off Interstate 8 in Alpine. The National Weather Service in San Diego predicts the high winds will start to abate by Friday morning, lessening to around 10 to 15 mph throughout most of the county. “Conditions are extremely dry and the relative humidities are down around 10%, which is very, very low,” said weather service meteorologist Philip Gonsalves. “The lower relative humidities are going to continue well into (Friday), even though the winds are weakening.” The recent round of Public Safety Power Shutoffs marks the first time since 2021 that SDG&E has employed the practice. Lines were de-energized in strategic locations five times in 2018 and 2020 and once in 2021. No shutoffs were instituted in 2022 and 2023, after two consecutive wet winters helped reduce the risk of wildfires in the region. Rural, backcountry communities in what is called the High Fire Threat District are particularly affected when their lines are de-energized because many homes there rely on water from wells powered by electricity for their homes, horses and livestock. Three Community Resource Centers have opened so that customers affected by the outages can get water, pick up snacks, charge their electronic devices and receive the most recent information regarding the shutoff. The center in Boulevard is located at 39223 California Route 94, the center in Descanso is located at the Descanso Branch Library at 9545 River Drive and the center in Protrero is located at the Potrero Community Center at 24550 California Route 94. All three centers are open from 8 a.m. to 10 p.m. Staff writer Christian Martinez contributed to this report.