Tag Archives: what temperature of water is too cold to swim in?

Cold Water Swimming Articles Index

Snow & Ice on the platform
Once you’ve swum during snow, you’re a true cold water swimmer

This post is an index with a very brief explanation of each of the specifically cold swimming related articles I’ve written, so one can scan the entire list for what is most relevant for their question or area of specific interest.

I was a bit surprised to see just how many I’ve written.

Articles sometimes tackle a similar area from a different angle, some focus on one small aspect of the cold-water swimming experience. This is a body of articles with which I’m quite happy.

If I could impart one simple message, it’s this:

Cold water swimming is dangerous, difficult and requires repetition to improve. No-one does it naturally or easily and knowledge is your ally.

By exploring the many aspects of cold; environmental, physiological and psychological, I hope to help you understand cold better and therefore become a more confident cold water swimmer. These articles therefore are intended to help swimmers adapt to cold water swimming.

It is really important to repeat that most of us are not naturally good at tolerating cold. (I certainly am not). Cold should be seen as something you train for, the same as any other aspect of your swimming.

The Ten Commandments of Cold Water Swimming. I am a prophet of cold water! :-)

The Golden Rules of Cold Water Swimming. For when Ten Commandments are too much.

Loneswimmer returns from the sea, with the commandments of cold water swimming
Loneswimmer returns from the sea, with the commandments of cold water swimming

Habituation. The process of getting used to getting into cold water. This is where it all starts and was therefore the first cold water swimming article I wrote.

Acclimatization. the process of developing tolerance for staying in cold water.

Introducing a Precise Open Water Temperature Scale. This site’s most popular article.

The Reverie of Cold. What I consider the best article on cold or maybe ever, that I’ve written.

“What temperature of water is too cold to swim in”. The most common search term leading into this site.

“What temperature of water is too cold to swim in” Redux. An updated version of the above post with a fuller list of factors affecting the answer.

I just can’t handle the cold“. Part 1Part 2 (What is the Vagus nerve and why is it important?), Part 3 (Fear). This is a phrase I hear a lot. Why this belief is irrelevant and why you, or I, are not special when it comes to cold.

WHY would anyone swim in cold water? Trying to answer the LEAST asked question about cold water swimming.

One of my hypothermia experiences. It happens to us all. That’s part of the deal.

Cold water and cold immersion shock, the first three minutes. It’s really important to understand what happens the body in the vital first few minutes of swimming in cold water.

The Worst Three Minutes. A not-often acknowledged aspect of cold water swimming.

How To: Prepare for cold water swim. Practical precautions around cold water swimming.

Prepare, Monitor, Recover. A short article on part of experienced cold water swimmers’ ethos.

Men, women and cold. Understanding gender differences in cold water exposure and tolerance.

Brown Fat vs. white fat. Interesting and very relevant recent scientific findings that have direct relevance to cold water swimmers.

Brown Fat. A revised version of the previous post.

Merino wool, my favourite cold weather clothes for per & post swimming.

The cumulative effective of cold water swimming. How it feels to swim in really cold water for many consecutive days.

Six hour swim in sub-eleven degree water. The second toughest swim I’ve ever done.

Christmas and New Year’s Day swim advice. Comprehensive advise for irregular swimmers in cold water. Applies to any irregular swims and swimmers.

coldExtreme Cold Water Adaptation in Humans. A five-part series trying to tease out all the various factors  of cold adaptation: Part 1 Asking the questions about individual variability, Part 2 (habituation and acclimatization), Part 3  (metabolic responses), Part 4 (further physiological responses), Part 5 (conclusion).

How we FEEL cold water. Concerning the body’s thermo-receptive response to cold water.

Always wear a belt. A lesson learned (and sometimes forgotten) about cold water swimming.

Peripheral vaso-constriction. The bodies primary physiological response to cold, in picture.

Wearing a watch. The primary safety device on cold water.

The important of stroke and the deficiencies of Total Immersion type swimming in cold water. Following the wrong advice for cold water is dangerous. Stroke rate is very important.

“Is the water too cold to swim”? Another different take on this popular question.

Winter. I like it. I hate it. The dichotomy of a cold water swimmer’s thoughts.

Come with me on this cold water swim. As close as I can take you to my experiences of swimming in cold water during the Irish winter.

Cold water swimming and the Second Law of Thermodynamics. Another experiential post of cold water swimming, with some musing.

Understanding the Claw. What is the Claw and why do cold water swimmers get it?

“Where did my Claw go?”  Further discussion on the Claw amongst experienced swimmers, the Claw being a common occurrence for cold water swimmers.

How To – Understanding Mild Hypothermia in swimmers. To address hypothermia, it is best to understand it. Mild hypothermia is more common than not amongst cold water swimmers.

How To – Understanding Moderate and Severe Hypothermia in swimmers. There’s nothing moderate about Moderate hypothermia.

How To – Diagnosing and addressing Moderate Hypothermia in swimmers. Understanding cold for support crew.

Speaking as a Coldologist… Analysing (and debunking) a claim to cold adaptation through meditation.

Cold water swimming and alcohol. They don’t mix and are a dangerous combination. This is important.

Ice Miles: My First Attempt, Part One (The swim). My First Attempt, Part Two (Post swim and analysis). My Second Attempt. Ciarán Byrne’s report of the successful Lough Iochtar Ice Mile.

What is Cold Water Diuresis in swimmers? Another physiological response to cold explained.

The relevance of shivering in cold water swimming. Yet another important to understand physiological response to cold.

The Magic Number. A consideration of transitional temperatures in cold water swimming.

The Magic Number

Cold water swimmers have a finely tuned thermo-receptive sense, an ability to judge water temperature reasonably accurately, just from how it feels on our skin. It’s something that develops with time, experience and swimming.

As an experienced pool manager my friend Clare told me that regular bathers will notice a temperature difference in warm water of half a degree. So you can imagine that cold water swimmers will probably have a similar ability.

I’ve written and often referenced my Precise Open Water Temperature Scale, one of this site’s most popular articles. It was a humourous attempt to convey some of that precision and personal experience. And the search term that still brings people in for this subject and is another of the site’s other most popular articles “what temperature of water is too cold to swim in“.

We refine this innate temperature-sensing ability as a result of regular immersion and the training of various aspects of the physiological response; habituation lowering our pre-immersion heart rate and eventually lowering stress hormones, and acclimatisation improving our cold exposure times, and we also get better at evaluating our thermo-receptive reaction. Of course you can only say that water feels like twelve degrees, if you have an actual thermometer so that you can do the comparison.

In those previous posts I’ve deliberately not put a precise figure on the question of what is too cold, because there are too many variables: the person experience, height and weight, the ambient air temperature and the local climate, the wind, the person’s drive to swim and more. I once read a Philippines swimmer say that water temperature of 21 degrees Celsius was too cold to swim. Of course the climate and ambient there is not just warm, but hot. Relatively cold water occurs at a higher temperature the higher the air temperature. The burden of constant cold for open water swimmers in Ireland, the UK and some other locations such as the Atlantic coast of South Africa, having no choice but to swim in cold water, is also an advantage, as we must acclimatise.

Nonetheless it is a fact that here in Ireland and in the UK and many other places such as the swimmers of San Francisco or Chicago, there is a Magic Number. That number is ten degrees Celsius, which (helpfully) is 50 degrees Fahrenheit. 10°/50° we could call it.

The Magic Number comes and goes. It goes when we get it in November or early December when the temperature is dropping and there’s rarely any temporary recovery. Once the water drops to 10°C, winter is here and there is little impetus to try to extend swims.

On the other hand we wait anxiously for the Magic Number to arrive, for the water to reach that level after the six long months of cold. The cold isn’t gone but at ten degrees hour-long swims can occur, often much more. Ten degrees, fifty degrees tease us more. The Magic Number may slide up for a weekend or a week only for the water to dip back to nine degrees again. It will probably, in a normal year, make its first appearance in April and dip again in early May.

Cold Guillamenes.resized.rotatedLocations that were out of reach over the winter are once more attainable. Tramore pier and back or Doneraile Head laps can resume. I can start swimming to the Metalman or around Brown’s Island again, each year like rediscovering those locations anew. The Sandycove swimmers will be double-lapping the island. Our swimming range extends and the world grows large again. 

At ten degrees Celsius, fifty degrees Fahrenheit, the watery world is ours once again.

What temperature of water is too cold to swim in? It’s not 10°/50°. That’s the Magic Number.

“What temperature of water is too cold to swim in?” Redux

Annual mean sea surface temperature from the W...
Image via Wikipedia

Apart from following specific swims of the Magnificent Seven, the post entitled “what temperature of water is too cold to swim in?“,  has for over a year been the site’s most popular.

This is a slightly updated version (main changes in italics), specifically the list of factors affecting ability.

This post was courtesy of searches on the site as a few variations of this question had cropped up.

I guess I could divide my thoughts on lowest possible water temperature in which to swim into three camps.

  • 1 degree WARMER than it is now
  • What it is now
  • 1 degree COLDER than it is now

Substitute any temperature reading into the above sentences…because cold is fairly subjective, (up to a certain point). I used to be in the first category, moved to the second, and am now definitely in the third. (All this means is I’ve (now) swam in 4 C. which makes me know it’s possible for me to swim in 2 C. It’s a moving target, last time those figures were higher).

I’ve pointed out before some of the things that affect your ability to deal with cold. Here’s the updated comprehensive list.

  • What weight are you?
  • What shape are you?
  • What shape are you in? (Fitness)
  • How did you sleep last night?
  • Are you tired just before you swim?
  • Have you drank alcohol in the last 24 hours?
  • Have you eaten (properly) today?
  • Are you well or ill?
  • Or have you been ill recently?
  • Have you swam in similar temperatures before?
  • If so, for how long?
  • If so, how often?
  • If so, how many times?
  • If so, how long ago?
  • Does Open Water scare you (just be honest with yourself)?
  • How well do you know the location?
  • Are you cold before you swim?
  • Is it sunny or cloudy or raining?
  • What’s the air temperature?
  • What’s the wind direction?
  • What’s the wind speed?
  • Is it choppy or calm?
  • What have the conditions been like for the last few days and weeks? And what are the prevailing conditions for your location?
  • How motivated are you?

So, as you can see, there are lots of variations just with these parameters. Some, like illness, are less likely but you really need to be aware of your own experience and take it incrementally.

One can’t reasonably expect to go from pool swimming to doing an hour in 7C / 45 F without a wetsuit, based on desire to swim alone. Granted, this isn’t likely to occur, but I’m trying to illustrate a point.
Ability to handle COLD is again a matter of a few factors being more important than others (all other things like alcohol, food, illness, sleep being equal): namely, experience and weight.

People with plenty of experience of cold can swim in very cold water. I can swim for 20 minutes in 5 C / 40 F water, because I’ve gotten used to it. But I certainly don’t recommend it and I won’t claim it’s fun. I’ve kind of changed my opinion on the fun aspect.  And the bigger and heavier you are the more you can handle with less training. Fat is an insulator. Just having plenty of fat alone makes cold easier to deal with. But fat does not lessen the pain of the initial shock for example.
The effect of wind is very significant. Any Northerly wind in Ireland is inevitably cold as may easterlies. Heat will be stripped from your body faster while swimming and while trying to get dressed. Any wind will generally cool you faster. And there is no thinking your way out of it out of wind. A similar effect is whether there is sunshine or not. Swimming the Guillamenes on a flat day which is calm, with no wind, warm air and sunny can lead to big difference than a choppy windy overcast day. even though the water may be no warmer, you can feel much more comfortable, due to the lack of wind combined with direct sunshine and calm water. I’ve said previously, wind is the swimmer’s enemy.

I can also tell you, without any embellishment, that my reactions to various temperatures are entirely different now than they were two years ago. I wrote a chart for myself of my reactions and estimated comfortable swim times at decreasing temperatures below 12 Celsius. That chart is now entirely useless as a current indicator, but is interesting to me as an measurement of how far my ability to handle cold has changed.

Some evidence says regular immersion in water temperatures of less than 10 Celsius is very beneficial for health, in a few different areas; improved respiration and circulation, lessened chances of infection and heart attack. However once the time goes over 10 minutes some of those benefits tend to reverse, especially hypertension and cardiac arrhythmia.

Update: Here’s my own scale of water temperatures and the possibilities.

If you are arriving here from USMS, board.ie or any of various pointers here, please note the Cold section on the top menu and you’ll find other more extensive writing on the subject.