Southern California's recent heat wave will intensify Wednesday with some areas experiencing triple-digit temperatures.
Desert and valley are forecast to eclipse 100 degrees Wednesday. Similar temperatures are expected through the weekend. Highs will be 8-18 degrees above normal. Expect the highest temperatures Wednesday in the Antelope, San Fernando and Santa Clarita valleys, and at lower mountain elevations.
Excessive heat warnings were issued Wednesday for Riverside and San Bernardino counties.
The late-summer heat arrived Tuesday when inland temperatures climbed above 100 degrees. The high temperature in Lancaster reached 105 degrees Tuesday.
The heat wave is caused by a combination of weak onshore breezes and a large area of high pressure building across Southern California, according to the National Weather Service.
"The added humidity could cause some discomfort with hot temperatures already in place," according to an NWS advisory. "Heat index values in some locations could approach critical levels."
Cooling centers open in the Santa Clarita area include the Valencia Library and Santa Clarita Valley Senior Center. In the Antelope Valley, the Lancaster Soccer Center and Desert Sands Park are open. Cinemark 12 is offering $1 movies for seniors.