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SAN DIEGO (CNS) – Temperatures soared into the triple digits Friday in parts of the San Diego area at the outset of an extreme late-summer heat wave expected to roast the region through the Labor Day weekend.

The predicted hot spell and accompanying low humidity and gusty winds out of the east prompted the National Weather Service to issue a “red flag” wildfire warning for the inland valleys and mountains, effective from 10 a.m. Saturday to 6 p.m. Sunday. The alert signifies a likelihood of critical combustion hazards that can lead to “extreme fire behavior.”

Air moisture levels will drop to the 15-20% range on Saturday and Sunday with poor overnight recovery, according to meteorologists. Winds out of the east are expected to reach sustained speeds between 15-25 mph, with gusts potentially reaching 30-40 mph in the southern reaches of the county.

Excessive heat warnings, meanwhile, will be in effect in the western valleys, the mountains and the deserts through 8 p.m. Monday; and in coastal areas from 10 a.m. Saturday through 8 p.m. Monday.

Friday afternoon, the mercury climbed into the high 80s along the coast and past the 100 mark in the inland valleys, mountains and deserts, the weather service reported.

Among notable thermometer readings as of 4:30 p.m., according to the NWS, were 97 degrees in Escondido and Julian; 98 in Santee; 99 in Alpine and San Pasqual Valley; 101 at Ramona Airport; 103 in Valley Center; 105 in Campo; 112 in Borrego Springs; and 115 in Ocotillo Wells.

To beat the heat, people should drink plenty of fluids, stay out of the sun during the hottest parts of the day and check on potentially at-risk relatives and neighbors, the NWS advised. Also, children, seniors and pets should be never be left unattended in a vehicle, with car interiors able to “reach lethal temperatures in a matter of minutes,” according to the federal agency.

To help residents escape the swelter, the county is offering nine air- conditioned “cooling centers” in Alpine, Borrego Springs, Fallbrook, Lakeside, Potrero, Ramona, Santa Ysabel, Spring Valley and Valley Center. Due to the coronavirus, mandatory mask-wearing and social-distancing protocols are enforced in the facilities.

A full list of the cooling center locations can be found here. All locations will be open from noon to 5 p.m. throughout Labor Day weekend.