LOS ANGELES (CBSLA.com) — The first heat wave of the summer revs up in earnest Thursday, raising wildfire concerns for hillsides teeming with rain-fed brush.

Temperatures are expected to climb 12 to 18 degrees above normal this weekend through at least the middle of next week, according to the National Weather Service.

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Beach communities will stay the coolest, but the Valley temperatures are forecast to be in the mid-to-upper 90s.

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Several watches, warnings and advisories will go into effect Saturday, when temperatures in the Inland Empire and high desert communities are expected to hit the hundreds and get even higher into at least Wednesday.

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People were urged to dress light, drink plenty of water, stay out of the sun, and check on friends and neighbors – especially seniors. Forecasters urged strongly against leaving children, seniors or pets in closed parked vehicles, even for a short time.