By Reginald Stanley. Posted June 7, 2021, 4:30 PM.

A low pressure trough moving over Southern California has spread cool temperatures, a deep marine layer and patchy drizzle across much of the region west of the mountains early this week, a trend set to continue through the middle of the week.

Daytime temperatures across much of the Inland Empire were cooler than average Monday, as a result from a stubbornly deep marine layer witch never fully burned off in some inland areas. Patchy drizzle was reported in some communities early Monday morning but no measurable precipitation was recorded at any WeatherCurrents station. Parts of the Temecula Valley, the surrounding foothill and mountain communities, as well as Riverside and even Simi Valley to the far northeast, have all seen temperatures struggle to climb out of the 60s as of Monday afternoon. Temperatures were somewhat warmer in Lake Elsinore, Hemet and Moreno Valley, while the warmest locations in the WeatherCurrents network on Monday have been the two high-elevation sites in Anza and Pinon Hills - an uncommon, although not unheard of scenario. The two aforementioned locations are outside of the marine layer's influence.

The trough is forecast to weaken by the end of the week, with temperatures returning to near seasonal norms over the weekend. Next week could see significant warming as high pressure builds over the region, sending temperatures above normal and raising fire weather risks.