Why Do We Swell in Summer and When Should We Pay Attention?

Swelling in hot weather isn't just something experienced by people with lymphoedema. So why does it happen, and what is our body trying to tell us?

Have you ever noticed that your shoes feel tighter at the end of a hot day? Perhaps your rings are harder to remove, your ankles look a little puffy, or your feet feel heavier than usual.

You're certainly not alone.

Many people experience some degree of swelling during warmer weather, even when they have no underlying lymphatic condition.

For some, it's a temporary response to the heat. For others, particularly those living with lymphoedema, the warmer months can bring more noticeable or persistent changes.

But why does this happen, and how do we know when swelling deserves more attention?

What's happening inside our bodies?

Our bodies are remarkably good at adapting to changes in temperature.

When we become warm, the small blood vessels near the surface of our skin widen. This process, known as vasodilation, helps our bodies release heat and regulate temperature. But there's another effect. As these vessels widen, more fluid can move from the bloodstream into the surrounding tissues.

Normally, much of this fluid returns to the circulation through the blood vessels, while our lymphatic system collects and transports excess fluid and proteins back towards the bloodstream. It's a process happening continuously, without us giving it much thought. However, when the amount of fluid entering the tissues increases, the body's fluid-management systems may have more work to do. And sometimes, particularly when we're standing or sitting for long periods, we begin to notice that extra fluid as swelling.

This is one reason why ankles and feet can become puffy on hot days.

Why doesn't everyone experience swelling in the same way?

You might spend a hot afternoon outdoors and notice very little change, while someone else finds their shoes becoming uncomfortable. That's because our bodies don't all respond in exactly the same way.

Age, circulation, medications, existing health conditions, activity levels and the amount of time spent sitting or standing can all influence swelling. Even the same person may notice differences from one day to another. Perhaps you've spent several hours sitting in the car, standing at a family gathering or working outside in the heat.

Your body may respond differently than it would after a day when you've been moving around regularly.

The important thing is recognising what's usual for you.

What makes lymphoedema different?

For someone living with lymphoedema, the lymphatic system's ability to transport fluid is already reduced or impaired. This may occur following surgery, cancer treatment, damage to lymphatic vessels or because of an underlying lymphatic condition. When warmer weather increases the amount of fluid entering the tissues, an already compromised lymphatic system may find it more difficult to manage the additional demand.

The result can be an increase in swelling, heaviness, tightness or discomfort.

And it's important to remember that lymphoedema isn't always immediately obvious.

Some people experience sensations of fullness, tightness or heaviness before significant swelling becomes visible.

Others may notice changes in the way their clothing, jewellery or footwear fits.

This is why paying attention to what you're feeling, not just what you can see, is so important.

Is summer swelling always something to worry about?

Not necessarily.

Mild swelling in both feet or ankles after prolonged standing in hot weather can be temporary and may improve when you cool down, move around or rest. However, we shouldn't automatically assume that swelling is simply caused by the weather. Swelling can have several causes, including medication effects, circulation problems and medical conditions that require assessment. New, unexplained, persistent or progressively worsening swelling should be discussed with a healthcare professional.

Sudden swelling, particularly in one leg, or swelling accompanied by pain, redness or warmth needs prompt medical assessment. Fever or feeling unwell alongside a swollen, red or hot area may indicate infection and also requires urgent attention. Swelling with chest pain or breathlessness requires emergency care.

For people already managing lymphoedema, recognising a change from their normal symptoms is particularly important.

Your body is giving you information

One of the things I believe strongly is that we need to become more aware of our own bodies. Not every change means something serious is wrong. But changes are worth recognising.

If your ankles swell after a long day in the heat, does the swelling settle overnight?

If you already have lymphoedema, are you noticing greater heaviness, tightness or discomfort than usual?

Are there particular activities, temperatures or times of day when your symptoms become more noticeable?

These observations can help you understand your body's responses and provide useful information to discuss with your healthcare professional. It's not about becoming preoccupied with every symptom. It's about recognising patterns, understanding when something has changed and knowing when to seek support.

Understanding is the first step towards taking action

Summer is a wonderful time of year in Australia. It's a time for family gatherings, holidays, outdoor activities, swimming and enjoying the longer days. And I don't believe that concerns about swelling should automatically mean missing out on those experiences. But understanding why swelling happens is an important first step.

When we recognise what our bodies are telling us, we're better placed to make informed decisions, seek appropriate advice and take practical steps to support our wellbeing.

Because the answer isn't to ignore swelling, nor is it to let the possibility of swelling stop us from enjoying life.

It's to understand what's happening and explore what we can do about it. And that's exactly what we'll look at in our next article.

Coming next: Don't Let Swelling Put Your Summer on Hold — What Can You Do About It?

Practical ways to stay comfortable, keep moving and make the most of the Australian summer, including simple activities and a personal summer wellbeing plan.