'Significant' SoCal Cooling Trend Brings Relief From Extended Heatwave

A "significant" cooling trend arrived in Southern California on Monday morning, promising a brief reprieve from the heat that has baked the region for the past several weeks, weather officials said.

The National Weather Service said a low-pressure system off Northern California will push cooler air into the region, dropping temperatures by several degrees each day through midweek. By Wednesday, valleys that saw highs in the 90s will dip into the upper 70s and 80s — as much as 10 to 15 degrees below normal. Coastal communities can expect 70s to low 80s, paired with deeper marine layer clouds.

The thickening marine layer will also deliver more widespread cloud cover, patchy fog, and even the chance for light drizzle along the coast and valleys Tuesday and Wednesday mornings. The NWS noted that the layer, currently around 1,000 feet deep, could expand to more than 3,000 feet by midweek, allowing clouds to push farther inland than in recent days.

From Monday through Wednesday, most areas are predicted to see temperatures 3 to 6 degrees lower than they have been, with coastal zones running 2 to 4 degrees cooler and valleys seeing as much as 12 degrees of cooling, forecasters said. Many areas will also see sundowner winds in the evenings, with advisory-level gusts possible in some communities.

The cooldown is expected to stick around through Thursday before another warming trend begins Friday into the weekend. Forecasters expect gradual clearing and a modest warmup as the low shifts south and a weak ridge builds overhead.

Temperatures are likely to rise a few degrees into Saturday, with some valley highs creeping back into the low 90s, though still slightly below seasonal averages.

Here are the highs expected on Wednesday across SoCal:

• Banning: 81 degrees
• Temecula: 77 degrees
• Palm Desert: 93 degrees
• San Diego: 74 degrees
• Santee: 77 degrees
• Carlsbad: 72 degrees
• Laguna Beach: 70 degrees
• Newport Beach: 72 degrees
• Mission Viejo: 75 degrees
• Long Beach: 75 degrees
• Rancho Palos Verdes: 73 degrees
• Los Angeles: 76 degrees
• Santa Monica: 69 degrees

The cooling trend arrives on the heels of last week's "surge of monsoonal moisture" and heat. Showers and thunderstorms coincided with the area's late-summer heat, bringing muggy conditions and raising wildfire concerns.

A heat advisory covered much of the Southland, with forecasters warning residents to avoid strenuous activity during peak afternoon hours and to seek air-conditioned spaces whenever possible.

Late summer heat has baked a region that experienced a relatively cooler start to summer, which forecasters called "No Sky July."