LOS ANGELES (CBSLA.com) — Triple-digit temperatures, an elevated wildfire risk and threats to public health will linger all week starting Monday as a dangerous heat wave sweeps through Southern California.

The heat wave is expected to peak by Monday afternoon with temperatures as much as 20 degrees above average and an excessive heat warning will be in effect through Wednesday night in the San Gabriel, Santa Clarita, San Fernando and Antelope valleys, the San Gabriel Mountains, the Santa Monica Mountain Recreational area and both coastal and inland Orange counties.

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Parts of the San Fernando Valley could see temps as high as 109 in Woodland Hills, while it will be slightly cooler along the beaches, with Long Beach hitting 90 in the afternoon.

Highs will be a bit lower in Orange County, with 80s at the beaches and as hot as 96 in Fullerton and Mission Viejo.

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Forecasters say the heat will linger through overnight hours and warn residents without air conditioning to brace for “significant heat impacts across much of southwest California”.

Hours are being extended at 13 cooling centers across L.A. for those without access to air conditioning.

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Angelenos were also advised to save energy during the heat wave to help avoid electricity shortages.