Los Angeles County’s top health official declared a “heat alert” this week and warned residents of the greater Los Angeles area, including the Santa Clarita, San Fernando and San Gabriel valleys, not to leave older adults, children or pets unattended in un-air conditioned homes or vehicles.

“It is critically important to never leave children, elderly people or pets unattended in homes with no air conditioning and particularly in vehicles, even if the windows are ‘cracked’ or open, because temperatures inside can quickly rise to life-threatening levels,” said Dr. Jeffrey Gunzenhauser, interim health officer of the Department of Public Health.

Gunzenhauser urged residents to help elderly or infirm neighbors without air conditioning get to local cooling centers or another air conditioned space during daylight hours.

“While it is very important that everyone take special care of themselves, it is equally important that we reach out to those who are especially vulnerable to the harmful effects of extreme heat, including children, the elderly and their pets,” Gunzenhauser said. “Extreme heat such as this is not just an inconvenience, it can be dangerous and even deadly.”

People who are frail or have chronic medical conditions may develop serious health problems leading to death, if exposed to high temperatures over several days, he said.

According to the Department of Public Health, schools and sports organizations should hold practice very early or late in the day to limit the amount of time athletes spend outdoors, and allow frequent rest periods and keep plenty or water or sports drinks on hand.

“When temperatures are high, even a few hours of exertion may cause severe dehydration, heat cramps, heat exhaustion and heat stroke,” Gunzenhauser said.

Health officials urged everyone to stay well hydrated and avoid sweetened drinks, caffeine and alcohol. Signs of dehydration include dizziness, fatigue, faintness, headaches and muscle cramps. Older adults and individuals on certain medications may not exhibit signs of dehydration until several hours after dehydration sets in, according to health officials.

High temperatures are expected to last through at least today. A list of cooling centers can be found at http://www.publichealth.lacounty.gov/docs/cooling-center.pdf or by calling the county information line at 2-1-1.