The National Weather Service in Fort Worth has extended its heat advisory. The heat advisory will now remain in effect until 8 p.m. Sunday.

High temperatures will range between 100 and 105 degrees, with heat index values around 105 each afternoon, according to the weather service.

"These hot conditions will increase the dangers of heat-related illnesses and fatalities," the weather service said in its advisory.

As a precaution, the weather service advises North Texans to check on people with health problems and the elderly, as they are the most susceptible to heat exhaustion and heat stroke.

"Never leave young children or pets in an enclosed vehicle, even for a short time," the weather service warned, "as temperatures can quickly rise to life-threatening levels."

To reduce risk during outdoor work, the Occupational Safety and Health Administration recommends scheduling frequest rest breaks in shaded or air-conditioned environments.

Anyone overcome by the heat should be moved to a cool, shaded location -- and an ambulance should be called.

"Heat stroke is an emergency; call 911," the weather service said.