An excessive heat warning denoting oppressively high temperatures will be in effect in the valleys and mountains of Southern California today as the heat wave gripping the region intensifies, raising fears of power outages resulting from high air conditioning use.
"High pressure will continue to build over the area this week, with the warmest days (of this week's heat wave) now expected to be today and Friday in most areas,'' according to a National Weather Service advisory.
Heat index values based on both temperatures and the humidity, which exacerbates high heat by adding an additional level of misery, will reach or surpass 105 degrees in many valley areas this afternoon and above 100 degrees in mountain areas below 4,000 feet, it said.
For example, while highs in the San Fernando Valley today will range between 98 and 108, it will feel like 105 to 110, according to the weather service.
"The combination of hot temperatures and high humidity will combine to create a dangerous situation in which heat illnesses are possible,'' according to the NWS advisory.
The excessive heat warning will be in effect from 11 a.m. today until 8 p.m. Friday in the San Gabriel, San Fernando and Santa Clarita valleys and the mountains of L.A County -- both the San Gabriels and the Santa Monicas.
The NWS issued these recommendations for coping with the heat:
- Drink plenty of fluids;
- Stay out the sun and in an air-conditioned room as much as possible;
- Check up on relatives and neighbors;
- Never leave children, the elderly or pets in an enclosed vehicle in the heat;
- If working outdoors, take frequent breaks where it's shaded;
- Anyone overcome by the heat should be moved to a shaded area, and 911 should be called since heat stroke is a medical emergency.
Also expected today, in the San Gabriels and the Antelope Valley, are winds gusting as high as 35 miles per hour accompanied by a slight chance of afternoon showers and thunderstorms, according to the weather service.
The latest seven-day forecast from the NWS indicates that temperatures will rise slightly in some localities Friday and generally start a slow downward trend Saturday.
On Monday, temperatures in some areas are expected to be 10 degrees lower than today.
While forecasters stressed the desirability of finding shelter in an air- conditioned environment, utility executives expressed concern about what it will do to the grid.
"High demand for around-the-clock energy use -- especially air conditioners -- could lead to failed equipment and power outages for Southern California Edison customers as high temperatures are expected through the weekend,'' the utility said in a statement issued from its headquarters in Rosemead.
"Many customers have been using more energy in the evenings because of the high temperatures, especially air conditioning, which is putting a strain on SCE's distribution equipment. This continuous use could result in the equipment failing.''
The utility said it has increased the number of crews available through this weekend as it braces for the possibility of outages, and it urged residents to conserve, including by setting thermostats no lower than 78 degrees and using electric fans instead of air conditioning when practical.