San Diego County is set to experience a significant shift in weather patterns this week as a persistent high-pressure system over the Southwest begins to weaken. According to the National Weather Service (NWS), current heat advisories for mountain and valley regions, along with extreme heat warnings for desert areas, are scheduled to expire at 8 p.m. Monday.
As the high pressure dissipates, residents can expect a gradual cooling trend beginning Tuesday. Coastal temperatures, which have been holding in the mid-80s, are forecast to drop into the upper 70s and low 80s by mid-week. Inland valleys will see a similar decline, with highs stabilizing in the 80s. Mountainous areas will experience the most noticeable change, transitioning from the upper 80s early in the week to the upper 70s by the weekend. Desert regions, while remaining warm, will see temperatures dip from the low 100s to the upper 90s.
The NWS notes that the cooling trend will be most pronounced from Wednesday through the weekend, with some inland areas potentially seeing daytime highs up to 10 degrees below seasonal averages by Thursday. Meteorologists also anticipate an increase in marine layer influence, which may bring night and morning low clouds and fog further inland.
In addition to the temperature shift, the NWS has issued a coastal flood advisory for county beaches, effective from 6 p.m. Monday until 11 p.m. Wednesday. Astronomical high tides are expected to exceed 7 feet between 8 p.m. and 9:30 p.m. daily. While surf heights remain low at 2-3 feet, the NWS warns that tidal overflow could impact low-lying beach areas, including parking lots.
Thunderstorm activity remains a possibility for the mountains and deserts through Wednesday, with peak chances occurring on Monday and Tuesday.