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Cold water swimming: Guide to temperature

Cold water swimming: Guide to temperature

One obvious difference between cold water swimming and indoor swimming is the temperature.

Open waters are much colder than an indoor pool, so you need to be aware of the risks that come with the icy waters.

Whether you’re a seasoned polar bear or an aspiring newcomer, understanding the effects of different water temperatures on the body is essential for a safe and enjoyable experience.

In this guide to temperature, we will delve into the fascinating world of cold water swimming.

Cold Water Swim explores the various temperature ranges, their impact on the human body, and the precautions to take.

So, let’s dive right!

Guide to water temperatures

In this guide to temperature, we will explore the different temperature zones that cold water swimmers encounter.

Our guide to temperature will discuss the effects these temperatures have on the body and assess the potential risks that cold water brings!

0 to 10 Degrees 

Swimming in cold temperatures, particularly between 0 to 10 degrees Celsius (32 to 50 degrees Fahrenheit), can have several health benefits.

However, it’s important to note that swimming in extremely cold water can pose risks. It’s crucial to exercise caution and take necessary precautions.

In the 0 to 10 degrees Celsius temperature range, the onset of hypothermia can occur more rapidly than in milder temperatures.

The body’s natural defences, such as vasoconstriction and shivering, may be less effective in maintaining a stable core temperature. As a result, swimmers need to be aware of the signs and symptoms of hypothermia.

When swimming in these temperatures, it’s important to take the right precautions. Wearing a wetsuit and a changing robe can be beneficial when swimming in these cold temperatures.

Wearing a wetsuit helps retain body heat in cold water, while a changing robe keeps you warm before and after swimming. Both provide insulation and protection from the cold.

0 to 10 Degrees
Freezing Lake

10 to 15 Degrees

Open water swimming in water temperatures from 10 to 15 degrees Celsius (50 to 59 degrees Fahrenheit) offers a unique and invigorating experience for cold water enthusiasts.

While still considered relatively cold, this temperature range is generally more tolerable for many swimmers and still provides the benefits of cold water swimming.

Many cold water swimmers find the 10 to 15 degrees Celsius range to be an ideal balance between the invigorating nature of cold water and the ability to sustain longer swims comfortably.

Swimming in this temperature range can provide a sense of revitalization, increased alertness, and a natural high that comes from challenging yourself in the water.

15 to 25 Degrees 

Up next on our guide to temperature, we have waters of 15 to 25 degrees Celsius.

Water temperatures ranging from 15 to 25 degrees Celsius (59 to 77 degrees Fahrenheit) are usually found in late spring/peak summer.

This range provides a more comfortable and enjoyable experience compared to colder water temperatures.

Swimming in the 15 to 25 degrees Celsius range is a wonderful opportunity to embrace the joys of water, connect with nature, and enjoy the benefits of swimming without the challenges associated with colder water temperatures.

So dive in, savour the experience, and make the most of your time in these pleasant waters.

15 to 25 Degrees
Women swimming in the ocean

25 to 30 Degrees

Water temperatures ranging from 25 to 30 degrees Celsius (77 to 86 degrees Fahrenheit) offer a warm and comfortable experience. It may resemble swimming in a heated pool or bath.

Although you’re unlikely to find these temperatures whilst outdoor swimming in the UK. You are more likely to find these temperatures in indoor pools!

Swimming in the 25 to 30 degrees Celsius temperature range compared to colder temperatures provides a relaxing and enjoyable experience. This temperature is perfect for leisurely swims, aquatic exercise, or simply unwinding in the water.

However, it’s essential to be mindful of your own preferences and the potential impact of prolonged exposure to warm water on your body.

If you start feeling overheated or fatigued, take breaks and cool down to maintain your comfort and well-being.


What are the risks of swimming in cold waters?

Swimming in cold waters can be an exhilarating and invigorating experience. However, it’s important to be aware of the potential risks involved, such as hypothermia, cold water shock, and afterdrop.

Cold water shock

Cold water shock refers to the immediate physiological and psychological responses that occur when the body is suddenly immersed in cold water.

It is a natural reaction triggered by a rapid change in temperature. Cold water shock can have serious consequences if not managed properly.

Here are some key symptoms of cold water shock:

  • Gasp Reflex (sharp intake of breath)
  • Breathlessness
  • Increased Heart Rate and Blood Pressure
  • Impaired Coordination and Muscle Function
  • Hyperventilation

Understanding the potential dangers of the cold water shock response and taking appropriate precautions are essential for staying safe during cold water activities.

It is always recommended to assess your swimming abilities, the water conditions, and your level of preparedness before entering cold water environments.


Swimming in water temperatures ranging from 0 to 10 degrees Celsius (32 to 50 degrees Fahrenheit) can potentially lead to hypothermia if proper precautions are not taken.

Hypothermia occurs when the body loses heat faster than it can generate it, resulting in a dangerously low core body temperature.

Prolonged exposure to cold water increases the risk of hypothermia. Mainly if the swimmer is not adequately dressed or if the water temperature is close to or below freezing.

In the 0 to 10 degrees Celsius temperature range, the onset of hypothermia can occur more rapidly.

The body’s natural defences, such as vasoconstriction and shivering, may be less effective in maintaining a stable core temperature.

As a result, swimmers need to be aware of the signs and symptoms of hypothermia, which include:

  • Intense shivering or cessation of shivering
  • Cold and pale skin
  • Slurred speech or confusion
  • Fatigue or lethargy
  • Loss of coordination or dexterity
  • Slow or shallow breathing
  • Weak or irregular pulse

If any of these symptoms are observed in oneself or a fellow swimmer during or post-swim, immediate action should be taken.

Get out of the water and seek warm shelter or call for medical assistance if necessary. It is crucial to remember that hypothermia can be life-threatening, and prompt treatment is essential.

Icy Lake


 “Afterdrop” refers to a phenomenon that can occur after a swimmer exits the water and experiences a further drop in their core body temperature.

It happens due to the delayed cooling effect of colder peripheral tissues that were exposed to the cold water.

When leaving the water, the colder peripheral tissues, such as the arms and legs, begin to warm up again, and the blood from these areas returns to the core. This process is known as rewarming.

As the colder blood mixes with warmer blood in the core, it can cause a drop in core body temperature.

The afterdrop effect can be more pronounced if you were exposed to extremely cold water or spent a long time swimming.

The drop in core temperature during afterdrop can lead to symptoms such as continued shivering and a prolonged sensation of coldness. You may feel very cold even when leaving the water after an open water swim.

How long should I stay in cold water?

As a general guideline, you should start with short swims of around 10 to 15 minutes in colder water. Then you can gradually build up to 20-30 minutes or more as you become more acclimated is a good approach.

However, it’s crucial to prioritize your safety and well-being and not exceed your personal limits.

Always be aware of the signs of hypothermia or other cold-related health issues and take appropriate action if necessary.

How long should I stay in cold water?
Woman immersed in cold stream

Are lakes or the sea typically colder?

Lakes tend to be colder than the sea because they are smaller, shallower, and have less water movement.

The sea is generally warmer due to its vastness, larger volume, ocean currents, and exposure to solar radiation.

Lakes are colder than the sea because they are smaller, shallower, and have less water circulation. These factors result in quicker cooling and temperature fluctuations in lakes.

Additionally, lakes in colder regions or at higher altitudes tend to have colder water.

The vastness and volume of the sea, along with ocean currents and solar radiation, contribute to its milder and more stable temperatures.

The ocean’s size allows it to retain heat better, and the movement of currents helps distribute warmth.


Cold water swimming can be a thrilling and invigorating experience. However, it’s essential to approach it with caution and respect for the potential risks involved. Our guide to temperature has covered all you need to know.

Understanding the effects of cold water on the body is crucial for staying safe and enjoying the activity to its fullest.

By following the recommended guidelines, such as acclimatising gradually, you can mitigate the risks associated with cold water swimming.

Remember always to prioritise your safety and well-being, and be mindful of water temperature, conditions, and your own comfort level.

Whether you’re swimming in lakes, the sea, or any other cold water environment, maintaining awareness, being prepared, and listening to your body are key.

Open water swimming can be a rewarding and transformative experience, providing a unique connection with nature and a sense of accomplishment.

So embrace the challenges, stay safe, and dive into the wonders of cold water swimming with confidence with our guide to temperature.