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With triple-digit temperatures expected to scorch much of Southern California this holiday weekend, forecasters are warning residents to prepare for potentially record-breaking heat.

A “significant warming trend” will begin Wednesday but temperatures won’t peak until Saturday and Sunday, according to the National Weather Service.

In Los Angeles and Ventura counties, an excessive heat watch will be in effect for all areas from Saturday to Monday, with temperatures of 100 to 115 predicted in non-coastal areas.

In Orange, Riverside and San Bernardino counties, an excessive heat watch will be in effect everywhere, except mountain areas above 5,000 feet, through Labor Day weekend.

By Saturday, triple-digit heat will likely be widespread across the region. The weather service is forecasting highs of 100 degrees for Los Angeles, 111 degrees for Santa Clarita, 105 degrees for Anaheim, 111 degrees for Riverside and 112 degrees for San Bernardino.

Meanwhile, extreme heat will also continue for the lower desert areas, which experienced its hottest August on record, according to NWS.

Palm Springs can expect highs of 115 degrees Saturday, while to the south, Thermal and Borrego Springs will likely hit 116 degrees.

But the hottest day of the intense, prolonged heat wave will likely be Sunday, according to forecasters.

The broiling start to September extends a sweltering August that saw dozens of records for daily highs either tied or broken across the region.

Forecasters warned that the prolonged heat wave could cause a range of dangerous impacts, including a higher risk for heat-related illnesses.

The weather service urges everyone to stay indoors when possible, avoid strenuous activity during the hottest part of the day, wear lightweight, light-colored and loose-fitting clothing, and drink plenty of water.

Never leave pets or children alone in vehicles — “look before you lock,” NWS stressed

Other major concerns include widespread and elevated risk of wildfires, and the increased threat of power outages.

California has been hit particularly hard during the 2020 wildfire season, which is already among the worst on record. As of Sept. 2, more than 7,100 blazes have charred over 1.6 million acres across the state, according to Cal Fire’s latest figures.

And a previous heat wave in mid-August prompted the state’s first rolling blackouts since the 2001 energy crisis, as excessive temperatures drove electricity use up and strained the grid.