It’s a common summer refrain: “It’s not the heat—it’s the humidity.” But is humidity alone really to blame for the discomfort of the summer months?
“It’s actually heat and humidity working together that our bodies don’t like,” says Robert Czincila, DO, chief of Emergency Medicine, Einstein Medical Center Montgomery. “High humidity, like we see in the Philadelphia region, gets in the way of the body’s ability to release heat. Combined with days or even weeks of high temperatures, this can be risky—even deadly.”
When it’s hot outside, our blood vessels circulate blood closer to the skin to help release excess heat and move water through the skin as sweat. But sweating by itself doesn’t cool the body unless it evaporates. In humid conditions, the surrounding air has an unusually high level of moisture, which prevents it from absorbing the sweat coming from our skin.
“When sweat isn’t evaporating from the surface of the skin, the body has to work even harder to cool down,” Dr. Czincila says. “It does that by producing even more sweat, increasing your heart rate and respiratory rate, and decreasing blood flow to the brain and other internal organs.”
This reaction affects almost every system in the body, from the cardiovascular and central nervous systems to joints and bones. Even worse, prolonged exposure to high temperatures and humidity can lead to a number of dangerous conditions, including heat exhaustion and heat stroke.
“Hot, humid conditions can quickly go from an annoyance to a health risk if we’re not making sure our bodies are able to cool off,” Dr. Czincila says. “We usually see an increase in emergency visits during heat waves, especially in periods when it doesn’t get cool enough at night to give our bodies a break.”
The easiest way to beat the heat/humidity combo is to avoid outdoor activity during the day when the sun is high, Dr. Czincila says.
“If you have to be in the heat and humidity, drink plenty of fluids, especially water, and wear light-colored clothing that allows air to circulate around the body,” Dr. Czincila says. “This will help your body cope with excess sweat that’s not being absorbed into the air.”
Dr. Czincila adds that even people taking these precautions should stay alert for signs of heat exhaustion in themselves and others.
“If perspiration stops, that’s a huge red flag that heat related illness is present,” Dr. Czincila says. “Before that, symptoms to look for include rashes, red or dry skin, muscle cramps, dizziness and confusion. If you or someone nearby experiences those symptoms, get out of the heat and seek medical attention.”