Excessive heat plagued Southern California on Sunday and more triple-digit temperatures are likely again to start the week.
The hottest temperatures were expected to be on Sunday and Monday as a hot air mass settles into place and high pressure builds. Temperatures in the triple digits will be common in the valleys, foothills and desert.
The heat wave comes as historic temperatures hit the Pacific Northwest, breaking all-time records in several cities.
Southern California beaches in the greater Los Angeles region are expected to see temperatures between 68 and 75 degrees, while inland valleys and mountains could reach 95 to 105 degrees. The Antelope Valley is forecasted to have temperatures as high as 112 degrees.
An excessive heat warning was in effect through 9 p.m. Monday in the
Antelope Valley, the Santa Clarita Valley and Los Angeles County mountains,
excluding the Santa Monica range. A less-severe heat advisory was in effect in the San Fernando Valley, forecasting high temperatures in the 90s to 105.
The high temperatures are expected to last into the week. A weather pattern with humidity and showers might develop between Tuesday and Thursday, according to the weather service, as monsoonal moisture moves over the area.
Elevated fire conditions are expected to be in place at least through Friday, and fire-starting lightning is possible Tuesday through Friday, the weather service reported. Fast fire growth could occur if a blaze starts.
Health officials urged residents to stay hydrated, wear sunscreen and lightweight clothing, beware of symptoms of heat stroke and check on vulnerable friends and relatives, such as the sick, older adults, pregnant women, children and those who live alone.
Los Angeles County library officials announced that the Lancaster Library, Quartz Hill Library and Acton Agua Dulce Library would be open until 10 p.m. Sunday and again Monday to serve as cooling centers. Information about cooling centers in the city of Los Angeles can be found here.
The California Independent System Operator, which runs the power grid, issued a heat bulletin Sunday in anticipation of increased electricity demand due to above normal temperatures across California -- and warned of a possible flex alert. But later the agency said there were no such plans because "projected resource deficiencies (were) addressed in the day-ahead market; there are now sufficient supplies to meet expected demand.''
But the agency also said it's continuing to monitor weather conditions and is asking Californians to stay prepared.
If weather or system conditions worsen, the ISO may notify the public about potential energy shortages and the need to conserve. The ISO could also issue a flex alert, a voluntary call for consumers to reduce electricity use during critical times of stress on the grid.