According to Edison's website, 308,046 customers were under consideration for shutoffs as of Wednesday afternoon.
Los Angeles and Ventura counties could see the most outages, with over 66,000 and over 94,000 customers affected, respectively.
The shutoffs are planned as the region expects to see a high potential for fire danger, with powerful Santa Ana winds and hot, dry conditions.
Cal State San Bernardino has announced that its campus will be closed Thursday in light of the high winds, fire danger and possible power outage.
Campus officials will decide Thursday whether to remain closed Friday, when similar conditions are expected. The latest campus alerts can be found here.
In San Bernardino County, over 63,000 customers could be left in the dark. The San Bernardino County Fire Department moved resources and personnel into position across the region, with several strike teams ready to respond should a fire break out.
INTERACTIVE MAP: Possible Southern California Edison power outage area
Residents across the region were gearing up for those potential power outages. Thomas Scott prepared his Rialto home for the worst by clearing his roof of pine needles to decrease the chances of wind-blown embers setting it on fire. He also has an evacuation plan.
Santa Ana winds, humidity can lead to fires spreading quickly
"We're looking at a recipe for an explosive fire. Should we get a fire that starts with wind on it to carry it from those ground fuels... into those now heavier fuels that are now dry and ready to burn," said the department's Eric Sherwin.
"Turning off our customers' power is not something we take lightly, but PSPS events are one of the ways we can better ensure the safety of the public, our customers, and our employees," Edison said in a statement.
Southern California Edison: Public Safety Power Shutoff - Am I Impacted?
According to the National Weather Service, a red flag warning is scheduled to begin at 1 a.m. Thursday and last until 10 p.m. Friday amid expected 20-40 mph winds across much of Los Angeles and Ventura counties.
Temperatures will climb as high as 93 degrees as relative humidity drops to between 2 to 9 percent.
Dangerous fire weather conditions for LA/VTA Mtns and valleys Thu-Fri as moderate-strong #SantaAna winds combine with hot temperatures, single digit humidities & very dry fuels. Rapid fire spread &extreme fire behavior could threaten life/property. #CAwx #SoCal pic.twitter.com/8wWr5X49hs— NWS Los Angeles (@NWSLosAngeles) October 23, 2019