Santa Ana conditions were expected to bring gusty northeast winds over the mountains and foothills of San Diego County Sunday the National Weather Service said.
The winds were forecast to weaken later Sunday, but very dry and warm conditions were expected to linger inland.
Cooling was expected to begin along the coast on Monday and progress inland through midweek as onshore flow strengthens ahead of another trough dropping south through Nevada, forecasters said.
A deepening marine layer may mean more clouds and fog over the coastal basin, with some drizzle possible by Wednesday night, the NWS said.
Temperatures were expected to be below average midweek, then rise back to average and above into next weekend.
High temperatures along the coast Sunday are forecast to reach 82 degrees, 88 in the western valleys, 83 near the foothills, 75 in the mountains and 91 in the deserts, according to the weather agency.
Low clouds and fog were rapidly dissipating Sunday morning near the coast as northeast winds increased.
“Some of that wind will mix down to the surface, especially along the foothills, helping to dry and rapidly warm the atmosphere,” forecasters said. “Very low relative humidity in these areas, coupled with the locally strong winds, will marginally increase the wildfire threat.”
Monday was forecast again to be very warm and dry, but the Santa Ana winds should weaken considerably.
Humidity inland was expected to remain near or below 15 percent with daytime high temperatures similar to Sunday. Temperatures near the coast were predicted to begin to moderate as a sea breeze develops Monday afternoon.
Northwesterly winds were forecast to gust around 20 knots in the outer coastal waters Sunday evening and again Monday evening.
— City News Service contributed to this article