By Andrew Hay

(Reuters) – A record heat wave with temperatures of up to 125 Fahrenheit (49 Celsius) was set to punish California starting on Friday as another extreme weather event raised risks of more forest fires and rolling blackouts.

The “deadly heat wave” of “rare, dangerous and very possibly fatal” temperatures was forecast across Southern California for the U.S. Labor Day holiday weekend, the National Weather Service (NWS) in Los Angeles said.

Record or excessive heat was also expected in Nevada and western Arizona with “brutal” temperatures set to peak on Sunday and continue into Monday, the service said.

“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.

Climate scientists blame human activities for a two to three degree Fahrenheit rise in average temperatures in California since the early 20th century and say extreme wet-dry cycles are creating abundant parched vegetation to supercharge wildfires.

The long weekend’s heat event is expected to be hotter than the one in mid-August that helped trigger the second and third largest forest fires in California history that are still burning.

Death Valley in California’s Mojave desert recorded one of the hottest air temperatures ever on the planet of 130F on Aug. 17, and highs of around 124F were expected there on Sunday, the NWS said.

The California power grid asked power generators to delay any maintenance until after the weekend to prevent blackouts like the two nights of rolling outages seen in mid-August as residents cranked up their air conditioning.

(Reporting by Andrew Hay; Editing by Tom Brown)