The increasing onshore flow was forecast to spread cooler and more humid air in inland San Diego County Sunday, the National Weather Service said.
Gusty westerly winds were predicted to develop over the mountains and deserts by Sunday afternoon, building the marine layer sharply into Monday morning when clouds and fog should reach the mountain slopes and passes. Some drizzle or light rain showers were possible west of the mountains.
Along the outer coast, areas of light showers and drizzle may be possible late Sunday night through Monday morning.
High temperatures along the coast Sunday were predicted to be 68-73 degrees with overnight lows of 52-57. Valley highs will be 73-78 with overnight lows of 45-53. Mountain highs were expected to be 67-73 with overnight lows of 38-46. Highs in the deserts will be 86-91 with overnight lows of 55-61.
Monday was expected to be the coolest day of the week with temperatures well below average and gusty westerly winds in the mountains and deserts, the NWS said.
Fair and warmer weather follows for the remainder of the workweek, with some coastal low clouds and fog during the nights and mornings.