Why Your Feet and Ankles Get Swollen During a Heat Wave

Heat edema causes swelling, often in the feet, legs and ankles, when the temperature skyrockets.
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For many people, summer days bring memories of barbecues, pools, beaches and lazy afternoons. But during prolonged periods of abnormally hot weather, unfortunate health problems can occur.

One such uncomfortable heat wave side effect? Heat edema, or swelling related to high temperatures. This water retention can be especially pronounced and obvious in the feet, ankles and legs due to the effects of gravity. Although usually temporary, this swelling may be uncomfortable, and, in some situations, may require medical attention.

Why Heat Edema Happens

Heat can cause temporary dilation blood vessels, and as a result, fluid can pool in the legs and feet, according to the University of Michigan. This extra fluid can make your skin tight and shiny and also cause swelling in the hands and fingers.

A sure sign you have edema is when an indentation remains after you press your finger into your swollen skin for several seconds. Heat edema tends to occur when the body is not already acclimated to the hot environment, according to the Mayo Clinic.

Certain medical conditions make people more susceptible to fluid retention and heat-related complications, including lung and heart disease, according to a June 2011 report in American Family Physician. Older adults, people who are overweight and pregnant women are also more prone to water retention. Heat edema also seems to be more common in women than men, according to the Centers for Disease Control and Prevention.

But even young, healthy, active folks may be at risk for heat-related swelling with limited access to air-conditioning or intense outdoor workouts in high heat.

Read more: 6 Surprising Symptoms of Heat Stroke and Heat Exhaustion You Need to Know This Summer

Preventing Swelling

To prevent heat-related swelling, avoid the extreme temperatures as much as possible. Keeping the body cool can minimize the dilation of blood vessels and prevent the accumulation of fluids in the legs. Drink plenty of fluids to prevent dehydration.

If you have to work outdoors in a hot environment or during a heat wave, take frequent breaks to cool down and gradually acclimate yourself to the weather. Avoid prolonged sitting or standing when possible, as staying sedentary can cause fluids to pool in the feet, ankles and legs.

When to Seek Medical Treatment

Mild swelling in the legs can typically be relieved by home care. Elevating the legs helps counter the effects of gravity on the feet, ankles and legs, facilitating normal blood and fluid flow. Brief walking and simple leg movements may also help ease the swelling.

While swelling in the feet and ankles during a heat wave usually isn't a major medical concern, it could be a sign of a more severe form of heat-related illness, such as heat exhaustion or heatstroke. And if your swelling is triggered by a medical condition, talk to your doctor about the best ways to relieve your edema.

Talk to your doctor if you have a sudden increase in swelling, or if you have edema for no apparent reason. Seek immediate medical care if you have swelling along with any trouble breathing or chest pain, warns the Mayo Clinic.

Read more: 8 Ways to Stay Safe and Cool During Summer Workouts

Is This an Emergency?

If you are experiencing serious medical symptoms, please see the National Library of Medicine’s list of signs you need emergency medical attention or call 911. If you think you may have COVID-19, use the CDC’s Coronavirus Self-Checker before leaving the house.