Californians sought relief on Friday from the first day of a punishing heat wave expected to last through the Labor Day weekend, bringing temperatures of up to 125 degrees Fahrenheit (49 Celsius) and raising the risk of wildfires and rolling blackouts. California Governor Gavin Newsom declared a state of emergency, a proclamation that allows power plants to operate beyond normal limits throughout the three-day holiday weekend. “The heat is on again! Please do your part to #ConserveEnergy to avoid power outages over #LaborDayWeekend. Some state beaches are closed or have modified operations due to wildfires & COVID-19,” California State Parks said on Twitter.The National Weather Service (NWS) forecast a heat wave carrying “rare, dangerous and very possibly fatal” temperatures across Southern California for the holiday weekend. “There is a high risk for heat illness along with heightened fire weather concerns,” the NWS Los Angeles office reported, forecasting record high temperatures on Saturday and Sunday.State officials urged Californians to turn off unnecessary appliances and lights to help avoid blackouts from an overwhelmed power grid. Authorities also asked power generators to delay any maintenance until after the weekend to prevent blackouts like the two nights of rolling outages in mid-August as residents cranked up their air conditioning.This weekend was expected to be hotter than one in mid-August that helped trigger the second and third largest forest fires in California history. Those fires are still burning. Death Valley in California’s Mojave desert registered one of the hottest air temperatures recorded on the planet of 130F on Aug. 17, and highs of around 124 were expected there on Sunday, the NWS said.Record or excessive heat was also predicted for Nevada and western Arizona with “brutal” temperatures set to peak on Sunday and continue into Monday, the weather service said.The NWS reported on Friday that Phoenix hit a new high for this date, registering 114 degrees at Phoenix Sky Harbor International Airport. The old record was 112 degrees set in 1945.Red flag warnings were issued for large swaths of the state, indicating a high fire danger.Climate scientists blame human activities for a rise in average temperatures in California since the early 20th Century and say extreme wet-dry cycles are creating parched vegetation to supercharge wildfires.