Break from Southern California heat wave will be short

Southern California will finally get a respite from the searing summer heat over the next few days, but it will be short-lived, according to the National Weather Service.

Temperatures are expected to be normal to slightly below normal in coastal areas and in the valleys through Wednesday, said Andrew Rorke, a meteorologist with the National Weather Service in Oxnard.

A marine layer returned Sunday and is expected to push temperatures down, Rorke said. During a heat wave, interior coastal air pushes the cooler air farther onto the water and keeps it from reaching land.

In downtown Los Angeles, the high temperature Monday is expected to be 84 degrees, Rorke said. Temperatures are expected to dip into the mid- to upper-70s Tuesday and Wednesday and then warm up Thursday as the high pressure returns.

Temperatures are expected to be around 88 degrees by the end of the week and “even hotter in the valleys” as a high-pressure system returns to the region on Thursday, Rorke said.

Last week, daytime highs in some inland communities reached triple digits. The summer heat also coupled with high humidity to drive the heat index up.

High humidity levels could be attributed to warm, wet air flowing up from the waters of Baja California that were pulled into the high-pressure area, Rorke said. Similar levels of humidity are not expected this week, he added.

Still, moisture and “instability lingering over the region” will bring a slight chance of thunderstorms for the interior mountains of Los Angeles County and the Antelope Valley through Monday evening, according to the weather service. The storms could produce lightning, gusty winds, brief and heavy rainfall and flash flooding.

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hailey.branson@latimes.com

Twitter: @haileybranson