Hot Temps to Continue Through Saturday in Claremont, La Verne

More sweltering weather was on tap for the Southland Friday amid warnings to residents to reduce their electricity use to avoid power outages.

Showers and thunderstorms may hit the Antelope Valley and the San Gabriel Mountains in Los Angeles and Ventura counties this afternoon, National Weather Service forecasters said.

Friday's temperatures will be 10-15 degrees higher than normal, according to the NWS, and overnight temperatures will also be unusually high as well, reaching 80 degrees in some areas in the foothills of the San Gabriel Mountains.

In Claremont, the NWS says the high can get up to 100 degrees.  In next door La Verne, the temperature can get up to 101, the agency said.

Saturday will also be a hot one in both cities, with temperature predicted to hit 98-99 degrees.

In some valley locations in Los Angeles County, the combination of high temperatures and low humidity will reach "critical levels" Friday, producing high heat index values, according to an NWS advisory. That means it will feel even hotter than what is indicated on the thermometer.

The high pressure blamed for the 3-day-old heat wave may weaken slightly Saturday and Sunday, but temperatures will remain above normal, according to the NWS.

Anyone planning to be outdoors in these hot, muggy conditions "should practice their heat safety," according to an NWS advisory. "Keep your body hydrated with plenty of water and avoid strenuous activity during the hottest part of the day."

Forecasters urge residents to make use of their air conditioners. But the Los Angeles Department of Water and Power asked customers to conserve energy use, especially during afternoon hours.

Energy demand in Los Angeles has climbed to a high range -- averaging in the upper 5,000-megawatts, according to DWP officials. This compares to an all-time high -- 6,177 megawatts -- recorded on Sept. 27, 2010.

Power outages have been minimal, but officials warned that outages are still possible as more people operate air conditioners and other appliances that must work harder to perform in high heat. They urged customers to limit energy use as much as possible between the hours of 11 a.m. and 6 p.m. Suggestions include:

• turning the thermostat up to 78 degrees
• limiting the use of appliances during peak hours
• closing draperies to keep sun out
• turning off lights and equipment when not in use
• opening windows to create ventilation
• unplugging "energy vampires" such as cellphone charges, DVD players, microwave ovens and other appliances that use energy even when turned off

The NWS forecast highs Friday of 79 in Avalon and Newport Beach; 84 at LAX; 87 on Mount Wilson; 95 in downtown L.A.; 96 in Long Beach; 98 in Anaheim and San Gabriel; 101 in Palmdale and Lancaster; 102 in Pasadena; and 105 in Woodland Hills and Saugus.

A slight cooling trend will start Saturday, but no real break in the heat wave is expected before Monday.

—City News Service contributed to this report.