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A heat wave is expected to hit Southern California Thursday and into Saturday, the National Weather Service reported.

An excessive heat watch is in effect for Los Angeles and Ventura County mountains and valleys Friday and Saturday, but temperatures will begin to rise starting Thursday, according to the weather service.

People prepare to cool off at Huntington Beach before a heat wave comes through Southern California on July 21, 2016. (Credit: KTLA)
People prepare to cool off at Huntington Beach before a heat wave comes through Southern California on July 21, 2016. (Credit: KTLA)

A high pressure system will form over Southern California on those days, resulting in high temperatures 10 degrees above what is normally the hottest time of the year.

Temperatures may reach up 100 and 110 in the valleys and lower mountains during the day with “only modest relief at night,” according to the agency.

The agency asks residents to take extra precautions if they work or spend time outside, and recommend that they reschedule strenuous activities to early morning or evening.

They recommend that residents were light-weight and loose-fitting clothing and drink plenty of water. The agency also urges pet owners not to leave their animals in inclosed vehicles, even for a short period of time.

The Los Angeles Department of Water and Power are asking customers to save energy during the heat wave.

High heat can also impact power reliability while residents and businesses use air conditioners all at once. Officials recommend that the most effective time to save energy is from noon to 6 p.m., when energy use is highest.

A cooling trend is expected Sunday and Monday, but high temperatures are expected again by the middle of next week.