The operator of the state's electric grid urged Californians to cut power consumption Tuesday and Wednesday, July 24-25 to help the region deal with a record-breaking heat wave.
The hot spell is the second of the month for San Diego. But this was the first time this year that the California Independent System Operator Corp. (CAISO) issued so-called Flex Alerts. The voluntary power cutbacks were in effect from 5 p.m. to 9 p.m.
Temperatures Tuesday ranged from the mid-to-upper 80s at the coast to the upper 90s and low 100s across inland valleys and foothills. Wednesday was to be the hottest day. Thursday would be only marginally cooler, said the National Weather Service .
Air temperatures near the water's edge were in the low-to-mid 80s on Tuesday and mid-to-upper 80s on Wednesday. If downtown San Diego reached 90 — that's 15 degrees above average.
"It's also going to be very humid at the coast because the ocean is so warm," said Alex Tardy, a weather service forecaster. In recent days, sea surface temperatures have reached or surpassed 75 in many spots, and San Diego Bay hit 80 over the weekend.
A large south swell also pounded local beaches this week, the biggest waves hitting North County. Some waves reached 6 to 8 feet. The waves will generate dangerous rip currents from Oceanside to Imperial Beach.
The heat wave that hit San Diego County in early July sent the temperature soaring to 117 in Ramona, the highest reading ever in that community.
"That heat wave was short and intense and had offshore winds," said Brian D'Agostino, a forecaster at San Diego Gas & Electric. "This heat wave will be longer and set daily heat records instead of all-time highs. And we're not expecting a lot of wind."
Anne Gonzales, a spokeswoman for CAISO, said the Flex Alerts in place were issued not only because of higher temperatures in California but in states across the West, which may affect electricity imports across the region.
"Normally, if we are in a heat wave, we can, say, get some electricity from the (Pacific) Northwest," Gonzales said. "However, when we see high temperatures across the western United States, then there's less chance of us getting imported electricity from other areas."
CAISO also cited tight natural gas supplies in Southern California and high wildfire risks.
Electricity consumers were urged to conserve power, especially between 5 p.m. and 9 p.m. when air conditioners hit their peak usage, as people come home from work. CAISO also urged consumers to delay running appliances such as dishwashers until after 9 p.m.
CAISO's conservation tips included:
• Setting thermostats to 78 degrees or higher and turn thermostats off if you are away;
• Using ceiling fans instead of air conditioning;
• Closing curtains, drapes and blinds to prevent sunlight from warming rooms;
• Turning off unnecessary lights and appliances;
• Using major appliances in the morning or late evening.
SDG&E has declared Tuesday-Thursday "Reduce Your Use" days, in which customers on the Reduce Your Use Rewards program receive a credit on their monthly bills by conserving energy from 2 p.m. to 6 p.m. About 80,000 customers have signed up for the plan.