Showers, Thunderstorms Forecast For San Diego County

SAN DIEGO, CA — Parts of San Diego County could see showers, thunder and lightning as monsoonal moisture moves over the region Sunday afternoon, according to the National Weather Service.

While the thunderstorms are expected to isolate over the county's mountains and desert regions, the rest of San Diego County is expected to remain shrouded under a thick marine layer, keeping temperatures unusually cool Sunday, according to the weather service.

"Going to the beach today? Little if any clearing is expected this afternoon," the National Weather Service tweeted. "A deep June-like marine layer is in place this morning, and has spread into much of the valleys."

Satellite imagery Sunday morning looked more like June than late August, with extensive marine stratus offshore, forecasters said.

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The cloud layer was thicker based on pilot reports and appeared to be deepening with even some spotty drizzle reports, which will ensure below-average high temperatures Sunday afternoon west of the mountains.

Despite the cool temperatures, lightning could increase the wildfire risk. The risk of thunder and lightning is expected to recede Sunday night only to return Wednesday, according to the weather service.

Farther inland, there were some low clouds Sunday morning in the San Diego deserts.

High temperatures along the coast Sunday were predicted to be in the mid-70s with overnight lows in the mid-60s. Highs in the western valleys were expected to be in the lower 80s, and in the upper 80s near the foothills with overnight lows in the lower 60s. Highs in the mountains were expected to be in the upper 80s with overnight lows in the mid-60s and highs in the deserts were predicted to be 94 to 104 with overnight lows in the mid-70s.

According to Accuweather, Sunday's high was expected to top out at 79 degrees in Poway, 77 degrees in San Diego, 79 degrees in Escondido, 74 degrees in La Jolla, and 77 degrees in Chula Vista.

Temperatures are expected to warm up slightly on Monday, according to Accuweather.

The days were expected to be noticeably warmer Monday and Tuesday, especially in the valleys as the marine layer thins. It's likely to be cooler again midweek as the marine layer deepens along with increasing clouds and humidity.

Drier air and building high-pressure Monday into Tuesday may limit any shower development, but a monsoon flow should return by Wednesday as high pressure weakens, renewing thunderstorm activity over mountain and desert areas.

Longer-range outlooks show hotter conditions toward the end of the month as an upper high becomes established over the southwest, forecasters said.

City News Service and Patch Staffer Paige Austin contributed to this report.