Dangerously hot weather will persist across much of the Southland Thursday, but temperatures are expected to begin falling ahead of a sharp weekend cooldown and the possibility of rain from moisture associated with Hurricane Rachel.
Extreme heat warnings will remain in effect through 8 p.m. Thursday for coastal and valley areas of Los Angeles County and coastal and inland Orange County, according to the National Weather Service.
Most areas are expected to cool 2 to 4 degrees Thursday, followed by a more noticeable drop of 4 to 8 degrees Friday that is expected to bring an end to the heat risk.
“Temperatures will trend cooler Friday into Sunday and there will be an increasing chance of showers and thunderstorms due to moisture from Hurricane Rachel,” the NWS said.
The forecast for Saturday will depend on Rachel’s track, but forecasters said increasing cloudiness and continued cooling are likely. Light rain could arrive in Los Angeles County as early as Saturday morning, although forecasters said Saturday night into Sunday morning is more likely.
An early-season cold upper-level low moving south from British Columbia is expected to bring a dramatic change in the weather over the weekend.
High temperatures are expected to fall another 4 to 8 degrees Sunday. Coastal and valley areas are expected to remain in the 70s.
An upper-level low moving over the Central Coast Monday, combined with remnant tropical moisture, could bring showers throughout the region and a 5% to 10% chance of thunderstorms.
Los Angeles County could receive around a half-inch of rain, while the eastern portion of the Los Angeles County mountains could receive up to 2 inches, forecasters said. High temperatures Monday are expected to range from the upper 60s to lower 70s.
Rain is expected to end by Tuesday, followed by decreasing clouds and warmer temperatures Tuesday and Wednesday.
Meanwhile, southerly swells, including those generated by Hurricane Rachel, will continue to create potentially hazardous conditions along the Los Angeles County coast.
A coastal flood advisory will remain in effect through 2 p.m. Tuesday.
Forecasters said the greatest concern will be Sunday, particularly during the morning high tide, with considerable to significant impacts possible at vulnerable beaches such as those in Long Beach.
The tide is expected to reach about 7.5 feet Sunday, although forecasters said the level could vary by about a half-foot depending on Rachel’s track.
Rachel is expected to turn northeast and accelerate, likely making landfall Sunday somewhere in northern Baja California or near the U.S.-Mexico border as a post-tropical system, according to the NWS.
Forecasters cautioned that the exact track remains uncertain and could affect the severity of coastal impacts.