Why Hot Weather Makes Your Feet and Ankles Swell

Warm weather means more sunshine, more sandals and for many of us, more swelling in the feet and ankles. If your lower legs puff up in the heat, you're not imagining things. It's likely due to a condition known as heat edema, which causes fluid retention in the body during high temperatures.

While typically harmless and temporary, swelling can be uncomfortable and sometimes even signal an underlying health issue. So, what causes this heat-related swelling, and how can you reduce it? Let’s break it down.

What Is Heat Edema?

Heat edema occurs when hot weather causes your blood vessels to dilate (or widen), which in turn allows fluid to leak into surrounding tissues, particularly in your lower body. Gravity plays a role here: fluid tends to pool in the feet, ankles, and legs when you’re standing or sitting.

You might notice:

• Puffiness in your feet or ankles

• Skin that looks shiny or feels tight

• An indentation when you press on the swollen area (a sign of “pitting edema”)

Fun fact: Heat edema is more common in people who aren't yet acclimated to warmer climates, according to the Mayo Clinic.

What Else Can Cause Swelling in the Heat?

Beyond warm temperatures, certain factors can increase your risk of heat-related swelling:

• Prolonged standing or sitting

• A high-sodium diet

• Pregnancy

• Premenstrual changes

• Certain medications (like those for blood pressure or diabetes)

• Underlying conditions such as thyroid disorders, heart failure, liver disease, or venous insufficiency

Even if you're otherwise healthy and active, long hours outside in hot weather especially without air conditioning can cause you to swell up by day’s end.

When Is Swelling More Than Just the Heat?

While heat edema is temporary, persistent or severe swelling could be a sign of another health issue. Some potential red flags include:

• Swelling that doesn't go away after rest and elevation

• Pain or redness in one leg (possible signs of a blood clot)

• Swelling accompanied by shortness of breath (which could signal heart or lung problems)

Doctors use a simple grading system to assess the severity of edema based on how long a finger indentation lasts in your skin. If your swelling regularly hits grade 2 or higher (lasting more than 15 seconds), it may be worth checking in with your provider.

How to Treat Swollen Feet and Ankles From Heat

If your swelling is caused by heat and not another condition it should resolve on its own once you cool off. These remedies can help speed up the process:

• Elevate your legs: Prop them up on pillows or rest against a wall.

• Try compression socks: These help promote circulation and reduce fluid buildup.

• Take an Epsom salt bath: Soothing and anti-inflammatory, these baths can ease swelling.

• Eat magnesium-rich foods: Think leafy greens, avocados, and nuts, which may help balance fluid retention.

Tips to Prevent Summer Swelling

Heat edema is largely preventable. Here’s how to keep your circulation strong and your ankles trim, even on the hottest days:

• Stay hydrated: While not a direct cure for edema, drinking enough water helps your body regulate fluids more efficiently.

• Keep moving: Avoid long periods of sitting or standing; walking around regularly helps prevent fluid from pooling.

• Reduce salt intake: Sodium encourages water retention—so skip the extra chips or processed snacks.

• Dress wisely: Lightweight, breathable clothing and open-toed shoes can help your body regulate heat better.

• Cool off: Find air-conditioned environments or use fans to help reduce body temperature.

When to Call Your Doctor

While most cases of heat-related swelling resolve with rest and at-home care, there are times when medical attention is warranted. If the swelling is painful, one-sided, or accompanied by symptoms like fatigue, dizziness, or shortness of breath, it could be a sign of something more serious, like heat exhaustion or a cardiovascular condition.

Persistent edema especially when unrelated to hot weather should also be evaluated, as it may indicate an underlying health issue that requires treatment.

Swelling in the heat might seem like just another summer annoyance, but it’s your body’s way of signaling that it needs a break and a bit of cooling down.

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