‘Tis The Season Day 10 – Temperature

That all important question to most people who ask me about swimming outside, whether it’s in the summer or winter is “How cold is it?”. And yes, temperature, and an understanding of it, is an important part of being a safe open water swimmer, even more so in the winter.

It’s not just about the temperature of the water though. The air temperature is just as, if not more important, than the water temperature. Near us the water temperature drops to around 4-6C in December and, with the exception of when ice covers the water, it hovers around that mark until the end of February and into March. That’s pretty consistent for 3-4 months. So is it just horrifically cold the whole time?

No. Obviously the water’s cold. But it’s at this time of year that the air temperature plays as big a part as the water.  Swimming in such cold water when the air temperature hovers around 10C is significantly easier than an air temperature of -2C on a grey day. When you’re body’s wet heat transfers rapidly to the surroundings. Cold air means more rapid cooling. You’re colder getting in and getting out and the few bits exposed to the air cool more rapidly whilst you’re swimming. November was a mixed bag of weather this year so whilst the temperature has slowly dropped, how cold a swim feels has varied massively. I swam in 4C water last week with an air temperature of 11C and it was significantly nicer than a swim I’d done a couple of weeks before in 8C water but with an air temperature of 1C. This combined affect of air and water has a huge impact on the effects on our body of winter swimming (‘Tis The Season Day 6 – Cold Water Effects)  but also on how we recover afterwards (‘Tis The Season Day 7 – The Joy of Lots of Layers). This air/water temperature combination was how the Short One almost got hypothermia last spring. We knew the water was cold but we’d misjudged just how cold the air was and how much that was going to affect us over a longish swim.

So, how do I measure temperature? I have three options;

  1. Thermometers. I have two, a cheapo one from the £1 shop and a significantly fancier wifi electronic BBQ probe (found in the bargain bin at Aldi). Both get used intermittently.
  2. Calum Macleans guide to water temperature. A hilarious summary of the different water temperature ranges. In fact, check out all his videos, they’re hilarious in many ways.  Calum Mclean – Guide to Water Temperature
  3. My own personal swearometer. The amount of swearing I do as I get in increases proportionally to a reduction in temperature.  Getting in at 10C in skins might illicit the utter of something mild, a crap or a bloody. Get down to 3C in skins and we’re talking foul mouthed filth you might expect to hear in a dockyard, plentiful F’s, often repeated like some kind of stuttering fool (sorry Mum!). It’s like my mind believes the repetition will distract me from the cold or illicit some kind of warming from the rapid intakes of breath. Wo betide the day there’s a family at the edge of our swim spot feeding the ducks and I have to reign in my foul mouthed habit.

Number 3 is undoubtedly the most used. The Short One can often take a good guess at how cold it is based on my sweariness. If you’re ever near water and the air turns blue it might be me heading in for a dip!


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