Dangerous heat wave to bring triple-digit temps

SAN DIEGO -- Record-breaking heat is expected to descend upon Southern California Monday, with temperatures ratcheting up over the next three days and remaining high but tapering off just a bit through the end of the week.

The National Weather Service has issued an excessive heat warning for San Diego County's inland valleys, western foothills and deserts that will be in effect until 10 p.m. Wednesday. A heat advisory is in effect in the mountains and along the coast, where temperatures will be cooler than the rest of the county but up to three degrees above the records for late August.

Meteorologists are predicting a high of 107 degrees Monday in Ramona, which would break the previous record high of 105 in the city for Aug. 28. Highs in El Cajon and Escondido are expected to reach 102, which would match the records in both cities for the date.

The heat wave, which is being caused by a "goliath" high-pressure system moving south from northern Nevada to southern Nevada, already reached San Diego County's deserts on Sunday.

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"Borrego set a new high temperature record (Sunday) at 116," the NWS tweeted. "The old record was 115 set in 2011."

And while the mercury will skyrocket Monday, temperatures are expected to be even higher Tuesday and Wednesday, with meteorologists predicting the heat to peak Tuesday for areas west of the mountains and on Wednesday farther inland.

On Tuesday, San Diego is forecasted to hit 91 degrees, which would break the previous Aug. 29 record of 88. Chula Vista is forecast to reach 95 degrees, one degree above the record for the date and 20 degrees above average, while Ramona is forecast to hit 108 degrees, besting the previous Aug. 29 high of 105. Chula Vista is also forecast to hit 92 on Wednesday, which would be four degrees higher than the previous record for the date.

The NWS predicts the weather will be "slightly less hot for Thursday into next weekend, but high temperatures will remain well above average."

High temperatures Monday will be 76 to 81 degrees at the beaches, 86 to 91 inland, 92 to 97 in the western valleys, 99 to 104 near the foothills, 94 to 100 in the mountains and 111 in the deserts.

"Persons working outdoors or those without access to adequate air conditioning will be more likely to experience heat related illness, such as heat exhaustion," the NWS said of those in areas under the extreme heat warning. "Some heat related illnesses are serious enough to require hospitalization and could become fatal if left untreated."

The weather service reminded residents to never leave kids or pets unattended in cars; drink more water than usual and avoid alcohol, sugar and caffeine; wear light colored clothing and a wide-brimmed hat outdoors to keep your head and body cooler; and take frequent rest breaks in shaded or air conditioned environments.