A National Weather Service excessive heat warning for the deserts took effect at 1 p.m., with temperatures topping 110 in some areas during the afternoon. A less severe heat advisory for the mountains and valleys also took effect, with both scheduled to expire at 9 p.m. Monday.
Because the toasty temperatures are expected to increase in the next few days, the county encouraged San Diegans to take advantage of “cool zones,'' designated public places with air conditioning that are scattered around the region.
One of those locations is the Borrego Springs Library, with extended hours until 7 p.m. today, 9 a.m. to 7 p.m. Saturday and noon to 4 p.m. Sunday. The library is located at 587 Palm Canyon Drive.
The NWS forecast a high temperature of 116 degrees Saturday and Sunday for Borrego Springs. Highs could even reach 120 degrees in some low desert areas, according to forecasters.
In San Diego, weekend highs are expected to be in the 80s at the coastline, in the 90s a short distance inland and close to 100 in the valleys.
National Weather Service meteorologist Brandt Maxwell told City News Service that the temperatures should begin to moderate by Monday along the coast, and Tuesday for the rest of the region.
“Actually, it looks like most of next week will be pretty nice,'' Maxwell said.
“We'll have a lot more of the marine influence -- we'll probably have some low clouds and patchy fog coming back,'' Maxwell said. “Once you get to about Tuesday, we should be back to what people live here for, the good weather.''
The NWS and county health officials are reminding residents to take precautions against dehydration, heat stroke and other heat-related illnesses this weekend.
Seniors, youngsters and pets lacking adequate shelter are most susceptible. Authorities also warned against ever leaving children, senior citizens or pets in parked cars, which can quickly become death traps in high heat.
Those working in hot areas were advised to reschedule strenuous activities, when possible; wear lightweight and loose-fitting clothing; drink plenty of water, but avoid sugary beverages; take frequent breaks in shaded or air conditioned areas; and watch for signs of heat exhaustion and heat stroke.
“Cool zones'' are generally libraries, senior centers and community centers that provide air-conditioned shelter while in operation, and are marked with a Polar Bear Cool Zone logo.
A full list of locations is available online at coolzones.org.