OCEANSIDE - Unusually warm weather throughout Southern California and a higher demand for energy Wednesday caused the organization that operates most of the state's power grid to ask users to conserve electricity.

At about 3:20 p.m., the California Independent System Operator declared what it calls a Stage 1 electrical emergency, in which the more than 30 million electricity users throughout California are urged to voluntarily limit their use of power, said Gregg Fishman, an Independent System Operator spokesman.

The Independent System Operator issues Stage 1 emergency alerts whenever the state's reserve of energy drops below 7 percent, said Fishman.

"We always maintain a 7 percent reserve margin going into a hot day," Fishman said. "We're starting to see the demand erode our reserve margin a little bit."

Although temperatures in coastal North County were primarily in the upper 70s Wednesday, a National Weather Service meteorologist said that high-pressure system bearing down on the southwest boosted temperatures in inland valleys to about 100 degrees - about 5 to 10 degrees warmer than usual.

Despite the heat, the Independent System Operator is urging customers to:

• set thermostats at 78 degrees or higher when home and turn off air conditioners when away from home;

• avoid using unnecessary lights and appliances between 4 and 6 p.m., which is the peak usage period; and

• turn off pool pumps and avoid outdoor watering.

Fishman said the Independent System Operator issued two Stage 1 alerts during an 11-day heat wave in July 2006. And on July 24, 2006, the organization issued a Stage 2 emergency alert, which is triggered when energy reserves drop below 5 percent, Fishman said.

During a Stage 2 emergency, power is cut to customers who have volunteered to have their energy supply interrupted during electrical emergencies. On July 24, 2006, Californians used a record 50,270 megawatts of power, Fishman said.

The Independent System Operator's Web site showed demanded peaking Wednesday at 48,530 megawatts, a bit higher than the 47,275 megawatt peak the organization predicted a day earlier.

On Tuesday, the Independent System Operator also issued a Flex Alert, which precedes Stage 1 emergency alerts, and also calls on customers to voluntarily reduce power usage.

Fishman said that the organization would have a better idea of how much electricity customers would use today by this morning. However, he said, another Stage 1 alert is likely based on Wednesday's predictions.

"A Stage 1 tomorrow is a pretty good likelihood," Fishman said. "We don't expect to get to a Stage 2 tomorrow."

Fishman said the Independent System Operator hasn't issued a Stage 3 emergency since 2001 when state residents faced rolling blackouts. Stage 3 alerts are triggered when reserves on the state's power grid drop below about 3 percent, which leads to rotating power cuts.

On Wednesday, temperatures throughout North County were quite warm, according to the National Weather Service. The mercury hit 104 degrees in Temecula; 101 degrees in Julian; 99 degrees in Ramona; 93 in Escondido; 90 in Fallbrook; 88 in Rancho Bernardo; 81 in Del Mar; 80 in Oceanside and 79 in Carlsbad, the Weather Service reported.

National Weather Service meteorologist Mike Lavis said the temperatures in most parts of North County would be two or three degrees higher today than Wednesday and the weather would remain that warm through the Labor Day weekend, with higher humidity in many places. Temperatures should cool next week, Lavis said.

The San Diego Gas & Electric Co. offers an advance notification program for anyone who's health would be at risk in the case of extreme heat, should rolling blackouts become necessary, according to its Web site. If the state were to call for rotating power outages, customers who sign up for the program would get an automated call giving them advance notice. Anyone interested in applying should call 1-800-411-SDGE (7343).

The elderly and disabled who are seeking relief from the heat can visit the utility company's cool zones, places where people can seek refuge from the heat during the afternoons while limiting the use of their own air conditioners.

The utility company and the county's Aging and Independent Services coordinate the cool zones, which are primarily in senior centers, according to the company's Web site. Transportation is provided to those who need it, the Web site states.

For a list of cool zones sites and other information, go to the Web site at: www.sdge.com/residential/assistance_services.shtml#coolzones

- Contact staff writer Keith Rushing at (760) 901-4151 or krushing@nctimes.com.