Punishing triple-digit heat continues to bear down on Southern California, with a fifth straight Flex Alert in effect today urging residents to conserve electricity during peak hours.

Excessive heat warnings remain in effect until at least 8 p.m. Tuesday for the mountains and the Santa Clarita, San Fernando and San Gabriel valleys, along with the inland coastal area, including downtown Los Angeles.

The warning in the Antelope Valley will last until 9 p.m. Wednesday, with temperatures anticipated up to 113 degrees.

On Saturday, record temperatures were recorded in Lancaster, Palmdale and Sandberg. Lancaster’s 109 was one degree higher than the previous record of108 set in 1955. Palmdale’s 106 tied the record set in 1947 and in the Antelope Valley community of Sandberg, Saturday’s 99 degrees broke the previous record of 97 degrees, set in 1955.

Sunday was shaping up to be even hotter, with highs of 102 expected in downtown Los Angeles, 107 in Pasadena, and 110 in Van Nuys and Santa Clarita.

In Orange County, excessive heat warnings are also in place through 8 p.m. Tuesday for coastal and inland areas and the Santa Ana Mountains and foothills. Forecasters said Orange County beaches will be in the upper 80s, with Santa Ana expected to reach 101 degrees, Anaheim 103 and Fullerton 104.

Overnight lows are not offering much relief either, staying in the 70s and even in the low 80s in some of the hotter areas.

“A prolonged period of very hot conditions with minimal coastal clouds is expected as high pressure aloft remains anchored over the West,” according to the National Weather Service.

“Triple-digit heat will be common for many valley and mountain locations through early next week. Record-breaking heat will produce a very high risk of heat illness.”

Authorities urged residents to drink plenty of water and only schedule strenuous activities in the morning or evening. Long Beach also opened several cooling centers throughout the city.

The California Independent System Operator—which manages the state’s power grid—issued the statewide Flex Alert from 4 to 9 p.m.

Residents are urged to take the following power-saving steps, including setting thermostats to 78 degrees or higher, avoiding use of major appliances, turning off unnecessary lights and avoiding charging electric vehicles.

The alerts have worked thus far, with the state avoiding involuntary power cutoffs. Officials said Sunday, Monday and Tuesday in particular are shaping up to be the most difficult days of the heat wave. Tuesday’s peak demand is forecast to be 50,087 megawatts, just shy of the all-time record of50,270 set in 2006.

According to Cal-ISO, electrical demand on Saturday was 45,829 megawatts, and the forecast for Sunday was about 45,000.

Triple-digit highs are expected to last through most of the week, with no significant cooling until Saturday.