LOS ANGELES (CNS) — A heat wave expected to last through Friday, Aug. 28, began rolling, threatening serious health conditions, especially for vulnerable residents,including the elderly and the homeless and what forecasters called an “elevated” risk of wildfire.

The valleys, especially the San Fernando and Santa Clarita valleys, will be Los Angeles County’s hottest spots. In both Woodland Hills and Saugus, highs of 101 degrees Fahrenheit are expected today, rising to 104 Thursday and 106 Friday before falling to 100 on Saturday, Aug. 29.

“The hot conditions may result in an increase in heat-related illnesses, especially for the homeless, elderly, infants, outdoor workers and those participating in outdoor activities,” warned an NWS statement, blaming the heat wave on “a strong ridge of high pressure.”

“The extended period of hot and dry conditions will also bring elevated fire danger,” it said.

Forecasters urged people to protect themselves and their loved ones from the high heat. They said residents should stay well-hydrated, avoid working in the sun, check on neighbors and relatives — especially the elderly — provide plenty of water to pets and livestock, and motorists must never leave children, the elderly or pets in closed cars parked in hot weather.

Los Angeles County health officials declared a heat alert for San Fernando, Santa Clarita and eastern San Gabriel valleys. County officials noted that cooling centers will be available throughout the county.

A list is available online at www.publichealth.lacounty.gov.