Another heatwave settles in as monsoonal moisture picks up for SoCal mountains

SAN DIEGO (FOX 5/KUSI) -- It's already been a hot summer and the heat continues into this week as another heat wave brings above normal temperatures for inland valleys.

Heat advisories have been extended for mountains and inland valleys through Thursday. 

San Diego Valley communities like El Cajon, Escondido, Poway and La Mesa are expecting daytime highs in the 90s majority of the work week with temperatures up to 100 degrees for the mountains.

In the deserts, an Excessive Heat Warning is in place the next four days due to maximum temperatures 109 to 115 degrees.

A ridge of high pressure above is trapping in heat each afternoon, primarily felt away from the immediate coast.

Beaches will top out in the upper 70s to low 80s this week and deal with a shallower marine layer.

Shifting towards monsoonal moisture, there will be chances of thunderstorms mainly in mountains and deserts through Wednesday, becoming more confined on Thursday.

Mid-level moisture increases Tuesday with a more southeasterly flow and could bring more widespread thunderstorm activity across our mountains. There could be heavy down...