A National Weather Service heat advisory is set to take effect at noon, Tues. Sept. 8 and extend until 6 p.m. Thursday in the valleys around Riverside.
High pressure could push temperatures in parts of Riverside County into the low hundreds today while showers and thunderstorms caused by tropical moisture will increase the risk of flash flooding throughout
the region. A flash flood watch for the mountains, the San Gorgonio Pass and the Coachella Valley will also extend from noon through Thursday evening.
Highs of 99 to 104 degrees are forecast today for the valleys, 88 to 95 degrees in the mountains and 104 to 109 along the San Gorgonio Pass near Banning and 105 to 110 degrees in the Coachella Valley. Highs of 100 to 105 degrees are expected in the valleys on Wednesday.
“High pressure aloft will bring hot daytime weather through Thursday with Wednesday expected to be the hottest day,” according to the weather service. “Nights will be warm as well with low temperatures 5 to 10 degrees above average.”
A chance of afternoon and nighttime showers and thunderstorms is also in the forecast through Thursday in most areas, and through Friday in the mountains. Forecasters said there is a 50 percent chance of measurable precipitation in the mountains, and a 20 percent chance elsewhere.
“Tropical moisture will continue to increase across far southern California into Thursday bringing an increasing chance of afternoon and early evening thunderstorms to the mountains, deserts and portions of the Inland Empire with locally heavy rainfall and flash flooding possible,” forecasters said.
Areas in and below recently burned areas would be particularly susceptible to heavy run off and debris flows should strong thunderstorms develop nearby.
Forecasters also urged people to protect themselves and their loved ones against dehydration, heat stroke and other heat-related illnesses. Residents were advised to stay well-hydrated, avoid working in the sun, check on neighbors and relatives — especially the elderly — and provide plenty of water to pets and livestock.