Sunrise on Sunday morning from Mount Woodson. Image from UCSD HPWREN camera

Excessive heat was forecast for San Diego County inland areas Sunday and Monday, while coastal areas remain under the influence of the marine layer, with patchy low clouds and fog each night and morning, the National Weather Service said.

Isolated light showers or thunderstorms may develop over the higher mountain peaks this weekend, with a better chance early next week, forecasters said.

The California Independent System Operator, called for another statewide Flex Alert from 4 p.m. to 9 p.m. Monday to avoid a possible shortage of energy as extreme heat in California and a growing wildfire in Southern Oregon threatens transmission lines, straining the state’s electric grid.

The agency, which manages the state’s power grid, declined to declare an alert on Sunday, after seeking two, from 4 p.m. to 9 p.m. Friday and Saturday.

A Flex Alert is a call for voluntary conservation in hopes of reducing strain on the system to prevent outages.

“CA, you did it! Your efforts helped keep the grid stable,” the ISO tweeted Saturday night.

The heat was expected to begin to ease on Tuesday as the upper-level high over the Southwest weakens.

Sunday’s highs were expected to be 116 to 121 degrees in the deserts, 92 to 102 in the mountains, 90 to 95 near the foothills, 71 to 76 along the coast and 77 to 82 farther inland.

Very hot weather, gusty southwest-to-west winds and minimum daytime humidity of around 15% was expected to create elevated fire weather conditions near and below the desert passes.

Isolated showers or thunderstorms may develop over the mountains Monday and Tuesday, the NWS said. Weakening high pressure may lead to cooler conditions beginning Tuesday.

Further cooling was expected to take place Wednesday through late in the week as the upper high weakens and splits and a weak upper-level trough develops along the West Coast, forecasters said.

Temperatures may finally return to near normal by Wednesday, even slightly below normal for the mountains westward on Thursday through Saturday.

Updated at 10:03 a.m. and 6:45 p.m. July 11, 2021

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