Why Your Feet and Ankles Swell in Hot Weather

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 summer weather can also lead to heat edema, the term for when your body swells in the heat due to water retention.

Heat edema can be especially obvious in the feet, ankles and legs because of the effects of gravity. Although usually temporary, this swelling may be uncomfortable, and, in some situations, it may require medical attention.

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Why Heat Edema Happens

Heat may cause swelling because it can temporary dilate (widen) the blood vessels, causing fluid to pool in the legs, feet, hands and fingers, according to the University of Michigan. This extra fluid can make your skin look tight and shiny.

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 is more likely to happen when you're not used to hotter temperatures, according to the Mayo Clinic.

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Beyond that, the following things can cause edema or make it worse, according to the Mayo Clinic and Cleveland Clinic:

  • Standing or sitting in one place for too long
  • Too much salt in the diet
  • Being pregnant
  • Having premenstrual symptoms
  • Some medications, including those to control blood pressure, diabetes or pain as well as drugs with steroids or estrogen
  • Certain diseases, such as kidney, liver, lung or thyroid disease, or congestive heart failure
  • Venous insufficiency, a condition where the valves of the veins in the legs become weaker

But even healthy, active folks may be at risk for heat-related swelling — especially swollen ankles and feet — if they have limited access to air-conditioning or do intense outdoor workouts in high heat.

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How to Prevent Swollen Feet and Ankles in the Heat

To prevent heat-related swelling, avoid extreme temperatures as much as possible. Keeping cool can minimize the dilation of blood vessels and help prevent fluid from building up in the legs.

If that's not possible, try the following:

  • Drink plenty of fluids to prevent dehydration
  • 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 swelling in the feet, ankles and legs
  • Avoid or limit salty foods

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Tip

Swollen feet after walking in the heat is common, per Harvard Health Publishing. To treat it, seek out a cool room where you can rest and elevate your feet to bring down the swelling.

When to See a Doctor

Mild swelling in the legs can typically be relieved with home remedies. Elevating the legs counters the effects of gravity on the feet, ankles and legs, helping with 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, per the Mayo Clinic.

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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.
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