Cooling Trend Hits Lake Forest After Year's Hottest Week: What To Expect

LAKE FOREST, CA — After several Orange County cities recorded their hottest temperatures of the year amid a stretch of heat running as much as 20 degrees above normal, a dramatic cooling trend is underway across the state, including in Lake Forest.

Starting Saturday, Lake Forest residents can expect temperatures to inch down to 87 degrees, with Sunday temperatures further lowering to 84 degrees.

On Monday, Lake Forest residents can expect temperatures to drop to 81 degrees, according to AccuWeather. Tuesday's high was forecasted to be 81 degrees.

The brief reprieve is a welcomed one after hot, humid temperatures scorched the region through the week.

And Lake Forest isn't the only place that felt the heat.

San Francisco reached 94 degrees Wednesday, San Rafael hit 104 and Oakland reached 97 while downtown Los Angeles hit 105, Long Beach reached 107 and Escondido hit 112 degrees, shattering the previous daily record for the date by 8 degrees. Each set or tied daily records, and each recorded its highest temperature of the year so far, AccuWeather reported.

In Orange County, Santa Ana reached 108 degrees, smashing the previous record of 103 set last year. Anaheim hit 107, breaking its previous daily record of 104, also set in 2024.

What's Behind The Temperature Swing

A strong area of high pressure over Southern California was a major factor. The ridge helped suppress the cooling influence of the Pacific while pulling tropical moisture from Hurricane Marie into the region, producing the unusual combination of extreme heat and high humidity, according to forecasters.

In Southern California, winds earlier in the week also favored hot air arriving from inland and desert areas rather than cooler air from the Pacific.

That pattern is now breaking down.

A low-pressure system moving south off the British Columbia coast and into the Pacific Northwest is weakening the ridge and strengthening onshore flow across California. That's allowing cooler Pacific air to push farther inland, pushing out some of the tropical moisture.

"The very hot and muggy weather has been the main story as of late, but today should be the last day of these truly oppressive conditions for Southwest Californians," the National Weather Service said Thursday.

NorCal Cools Off

For the Bay Area, the change has already been dramatic.

The developing low helped bring back a marine layer roughly 500 to 1,000 feet deep, according to the National Weather Service.

By early Friday, temperatures across the Bay Area were running roughly 5 to 25 degrees cooler than they were 24 hours earlier, forecasters said.

The marine layer is back and current temperatures are 10-20 degrees cooler than 24 hours ago. #CAwx pic.twitter.com/ROJ6iZ4uMn

— NWS Bay Area 🌉 (@NWSBayArea) September 11, 2026

Friday highs were expected to reach the upper 60s to lower 80s around the bay, with mid-80s to lower 90s in inland valleys. Temperatures along the immediate Pacific coast were expected to remain mainly in the lower to mid-60s.

The cooling will become even more pronounced over the weekend.

Bay Area inland highs are expected to fall into the mid-70s to mid-80s, while areas near the bays should generally reach the upper 60s to upper 70s.

Temperatures around the Bay Area should remain near or slightly below seasonal averages through much of next week.

Relief For SoCal On The Way

Southern California will take a little longer to completely shake the heat.

Temperatures in downtown Los Angeles were still expected to approach 90 degrees Friday, several degrees above normal, according to AccuWeather.

Extreme Heat Warnings were scheduled to remain in effect until 8 p.m. Friday in the Coachella Valley and San Gorgonio Pass, while Heat Advisories covered much of Orange, Riverside and San Diego counties.

Friday highs were expected to range from the upper 70s to mid-80s near the coast to the 90s in the Inland Empire. Low desert communities could still reach 106 to 110 degrees, according to the National Weather Service.

But each day through the weekend should bring additional relief.

By Sunday, highs should fall into the mid- to upper 70s near the coast and upper 80s to lower 90s across the Inland Empire. Lower desert communities will remain hot, with highs of roughly 102 to 106.

For many inland valleys, Sunday's temperatures could run about 5 degrees below normal.

Los Angeles County will see a similar shift, with most coastal areas settling into the 70s and many inland communities in the 80s over the weekend.

"By this weekend, highs will be near average across much of the Southwest, but humidity levels may remain elevated, especially in Southern California," AccuWeather Senior Meteorologist Dave Houk said.

The coastal marine layer will also make a comeback. Night and morning low clouds are expected to become more widespread from Orange County south through San Diego County and could push into some western valleys as the marine layer deepens.

Looking Ahead To Next Week

The cooler pattern is expected to last through at least the middle of next week across much of California.

Another ridge of high pressure could begin strengthening during the latter half of next week, potentially starting another warming trend in Southern California.

Forecasters, however, do not currently expect that warming to rival this week's record-breaking heat.