San Clemente and other South Orange County coastal areas can expect some relief from extreme heat warnings by Thursday evening, though dangerous heat persists today across inland regions. The National Weather Service reports that extreme heat warnings remain in effect through 8 p.m. Thursday for coastal and inland Orange County, as well as for coastal and valley areas of Los Angeles County.
Forecasters indicated that strong high pressure aloft continues to impact the entire West Coast, leading to dangerously hot daytime temperatures and very warm overnight temperatures in many areas. While the cooling today is expected to be largely confined to coastal areas, valleys and other inland areas will see little or no change, according to the National Weather Service.
The good news, forecasters said, is that onshore flow is gradually returning. This shift is expected to bring at least a 1-3 degree cooling trend for most areas through the end of the week. A more significant cooling trend is projected to begin on Friday. Although temperatures will still be about 5 to 10 degrees above normal on Friday, they are anticipated to fall below the levels that necessitate additional heat warnings or advisories.
An even sharper change in weather is expected from Sunday through Tuesday. A cold low-pressure system moving south from Canada is predicted to send temperatures below normal across the West Coast during this period. By Monday, high temperatures are expected to be mostly in the 70s, which is approximately 5 to 15 degrees below normal, according to the National Weather Service.
Beyond the heat, forecasters are also monitoring moisture associated with Hurricane Rachel. This moisture could move into Southern California, potentially bringing showers late this weekend or early next week. The National Weather Service noted there is at least a 5-10% chance of thunderstorms on Sunday or Monday, given the latest forecast track showing the remnants of Rachel moving slightly farther north than before.
Separately, a southerly swell generated by Hurricane Rachel is creating potentially hazardous conditions along the Los Angeles County coast, including Catalina Island. A coastal flood advisory for these areas is in effect from 6 a.m. Wednesday through 11 p.m. Friday. Forecasters have specifically warned that flooding impacts could be greatest in Long Beach, particularly the Alamitos Peninsula, as well as Catalina Island and the Malibu and Zuma Beach areas.
The swell will initially approach from the south-southeast before becoming more southerly from Wednesday through Friday. During this advisory period, morning and evening high tides are expected to range from 6.5 to 7 feet. Conditions could become even more hazardous over the weekend and into early next week, when tides exceeding 7 feet are expected to combine with multiple swells arriving from both the south and west. Forecasters acknowledged significant uncertainty regarding the timing and magnitudes of these swells, which leads to uncertainty in exact coastal flooding and surf impacts. However, they also cautioned that "there is a risk for significant impacts."
