The marine layer early Thursday morning was around 3,500 feet deep in San Diego County, the National Weather Service said.
The greatest concentration of light measurable amounts from drizzle through 4 a.m. Thursday was for coastal and western valley locations in northern San Diego County, the NWS said.
Patchy drizzle was expected to continue into Thursday morning for coastal areas into the western valleys.
Along the coast Thursday, it was expected to be partly cloudy with high temperatures from 70 to 74, the NWS said. The valleys were expected to be mostly cloudy with highs from 71 to 74. Mountains may be partly cloudy with highs from 72 to 82. The deserts were expected to be mostly sunny with highs from 97 to 101.
The marine layer was predicted to gradually decrease in depth Friday and Saturday to 2,500 to 3,000 feet with night and morning coastal low clouds extending well inland and across much of the valleys.
A slight chance of showers and thunderstorms continues for Friday afternoon.
The warming trend, greater for inland areas, was expected to continue into Saturday.
For Sunday and Monday, a large low pressure system moving inland along the West Coast could strengthen the onshore flow, spreading cooling inland.
Warming was expected for Tuesday and Wednesday, but with high temperatures for the mountains and inland valleys still around 10 degrees below average on Wednesday with lower elevations a few degrees below average.
