California has a history of power lines sometimes sparking wildfires during high wind conditions, so utilities are responding in elevated fire risk situations by taking a proactive measure — turning off the electricity.
Last week, Southern California Edison temporarily shut off power to thousands of people in Riverside County for some 33 hours in "extremely high-wind areas" to keep its electrical lines from sparking a wildfire.
Also, San Diego Gas & Electric cut power to a mountainous area in southeastern San Diego County last week when major portions of Southern California were in red flag alerts, indicating dangerous fire weather.
"De-energizing is an important tool to protect the safety of the communities we serve," SDG&E spokesperson Christy Ihrig told CNBC. The utility is part of San Diego-based Sempra Energy.
SDG&E has a network of more than 170 remote weather stations with wind sensors that allow it to identify locations where there are very strong wind gusts, sometimes in excess of 80 miles per hour.
The drastic step of cutting power to residents comes as California is coping with one of its worst wildfire seasons ever and as firefighters battle the monster Thomas fire in Ventura and Santa Barbara counties.
"The evidence is that a lot of the big fires we've had have happened on windy days," said William Stewart, a wildfire expert and co-director of University of California-Berkeley's Center for Fire Research and Outreach. "Power lines are one source of ignition. Even if there's a car wreck on a windy day it can do the same thing."