But, Gambino cautioned, "do not use a fan in a closed room, because it will create a convection-oven effect."
Those most vulnerable for heat stress include small children, those with chronic medical conditions, people who work outdoors, and the elderly, according to area health officials.
The warning signs include loss of energy, loss of appetite, nausea, light-headedness, and heavy sweating.
But "those at risk in the heat shouldn't wait for a warning," urged Philadelphia Health Department spokesman Jeff Moran. "They could take precautions to avoid exertion when it's hot."
In the case of a medical emergency, Moran said, sufferers should call 911.
So far this year, there have been four heat-related deaths in the city.
On June 2, a 50-year-old man was found at Eighth and Walnut Streets in Center City with a core body temperature of 105, the starting point for hyperthermia.
On June 3, a 77-year-old man was found in his second-floor bedroom, with all his windows shut.
On June 28, a 46-year-old woman was found in her bedroom also with the windows closed. That same day, an 88-year-old man was found in his first-floor bedroom, windows closed, and a fan blowing.
Moran urged neighbors and caretakers to check on those most at risk during the lingering heat wave.
If there is a heat advisory, 13 Delaware County senior centers will extend their hours and check on at-risk patrons, said Louis G. Colbert, director of the County Office of Services for the Aging.
In Upper Darby, the Health Department will monitor the heat and make necessary adjustments, said assistant director Matt Verdi. That includes possibly opening "a comfort station" in Upper Darby High's cafeteria, serving water and snacks to those needing to escape the heat.
Health officials also advised people to avoid caffeine and alcohol. Both cause the body to lose water more quickly, leading to dehydration.
