Simmer down now, people.

The first day of summer is Monday. And Mother Nature will probably let you know it in no uncertain terms.

It could be the hottest day of the year so far.

“A truly historic heat wave is likely to bring intense and all-time record–challenging heat to a large part of the Southwest this weekend into next week,” said AccuWeather senior meteorologist Ken Clark.

Death Valley could reach a near-record 130 early next week, the forecaster said in a statement. Palm Springs could see 117.

A high-pressure system is building over the Southwest, forecasters say. It will really start to rock your world over the weekend.

Until then Pacific on-shore flow will keep the Westside and much of the basin cool, with below-normal temps expected, forecasters said.

By Friday, L.A. valleys and foothills could see high temps in the upper 80s, according to the National Weather Service. Saturday they'll continue to climb, the NWS said.

Sunday (Father's Day) through Tuesday, temperatures will flirt with 100 in the L.A. Basin, with valleys ranging from 100 to 112, federal forecasters said. 

“Several daily and even monthly records could break on Monday,” the National Weather Service said in a statement. “By Monday, highs will generally be in the 100 to 110 range away from the coast. Overnight temperatures will also be above normal, with mid-60s to mid-70s common by next week. Excessive heat warnings look likely on Monday.”

Awesome. There is respite, however.

“The heat will have thousands flocking to Southern California beaches for relief, where temperatures will be significantly lower and patchy low clouds are likely,” AccuWeather states.

The usual warnings apply: If you're old, frail, in bad health, super white (hi, Mom!) or just plain out of shape, take it easy.

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