Prolonged exposure to heat during a humid day as opposed to a dry one prevents the body from naturally cooling through sweat.
“The body cools down primarily by the evaporation of sweat on the skin,” he said. “When the air is dry, sweat evaporates and cools the skin. When the air is humid, sweat doesn't evaporate as well and the body is unable to cool down.”
To offset the stress caused by heat, staying hydrated is a key factor, along with wearing loose-fitting, light-colored clothing and protecting the skin with sunblock when outdoors.
Acclimating the body to warmer weather takes time, he added.
“Heat acclimatization is the process of increasing your body’s core temperature so that the body sweat earlier and in greater qualities,” Danesh said. “This allows the body to cool at lower temperatures and more effectively.” Older people living in hot apartments without air-conditioning are at the highest risk for heat stroke, he said.