Triple-digit dry heat was expected Monday and Tuesday in the Redlands and Loma Linda area, with slightly cooler temperatures in the mountains.
Highs in inland valleys were expected from 100 to 108 degrees Fahrenheit, according to the National Weather Service.
"High pressure aloft over California will bring additional warming today . . . with high temperatures generally 10 to 15 degrees above average for most inland areas," the Weather Service advised Monday morning. "Except locally around 20 degrees above average in portions of the Inland Empire and inland Orange County."
The Weather Service estimated highs for Oct. 1:
INLAND VALLEYS . . . 100 TO 108.
MOUNTAINS BELOW 6000 FEET . . . 85 TO 100.
MOUNTAINS ABOVE 6000 FEET . . . 75 TO 85.
UPPER DESERTS . . . 90s TO 102.
LOWER DESERTS . . . 106 TO 112.
Anyone planning to be outside "in the heat during the late morning and afternoon hours should stay hydrated and know the symptoms of herat exhaustion and heat stroke," the Weather Service advised. "Drink plenty of non-alcoholic and non-caffeinated fluids and avoid strenuous outdoor activity if possible."