Widespread rain and possible thunderstorms are headed for Southern California this week, with forecasters on Monday warning that some areas could receive up to 2 inches of rain.
The National Weather Service said a low-pressure system moving south along the California coast will bring cooler temperatures ahead of the rain.
“Still looking at a good chance of our first traditional storm system of the season Wednesday and Thursday,” according to the NWS. “Timing still an issue but for now it looks like Wednesday will primarily be light rain, then transitioning to more of a convective/showery system overnight into Thursday.”
Forecasters said Los Angeles County could receive between three-quarters of an inch and 1 inch of rain, with totals reaching 2 inches in foothill areas and along coastal mountain slopes.
There is also a 25% chance that rainfall amounts could exceed those projections, according to the weather service.
The storm is expected to bring approximately 12 hours of rain to the Los Angeles area, along with a slight chance of thunderstorms.
Forecasters said rainfall rates generally are not expected to be hazardous unless thunderstorms develop, potentially producing locally heavier downpours.
Rain could begin as early as Tuesday night, although the latest forecast suggests Wednesday will bring lighter precipitation before showers become more widespread overnight into Thursday.
In Orange County, the NWS is also forecasting showers and a slight chance of thunderstorms, with the greatest likelihood of precipitation Wednesday night through Thursday morning.
The developing storm will bring a significant cooling trend to both counties, following several days of unusually hot weather and powerful Santa Ana winds.
Temperatures began falling over the weekend as offshore winds weakened, and additional cooling was expected Monday and Tuesday.
Los Angeles County coastal and valley communities will experience another 4 to 8 degrees of cooling Tuesday, with most afternoon temperatures dropping into the 70s.
Cloud cover will increase as the storm approaches, with marine layer clouds also expected along portions of the coast.
Wednesday and Thursday are expected to be cloudy and cool across much of Los Angeles County, with afternoon highs generally in the mid-60s to lower 70s.
Orange County will also experience cooler weather, with coastal highs generally in the lower to mid-70s Wednesday, falling into the upper 60s to around 70 Thursday.
The low-pressure system is expected to move south along the California coast before shifting inland, producing rain and potentially isolated thunderstorms as it crosses the region.
Rain is expected to taper off in Los Angeles County by Thursday evening or shortly after midnight, followed by clearing skies Friday.
Temperatures should begin recovering Friday, with highs rising 3 to 6 degrees in many Los Angeles County communities, although conditions will remain cooler than normal.
Additional warming is expected over the weekend, when weak to locally moderate Santa Ana winds could develop.
Meanwhile, a beach hazards statement remains in effect through Tuesday morning for portions of the Los Angeles County coastline.
Forecasters said surf of 3 to 6 feet, particularly along south- and southwest-facing beaches, could produce dangerous rip currents, minor beach erosion and isolated tidal overflow in low-lying areas.
The weather service urged beachgoers to exercise caution around the elevated surf and dangerous currents.