What is the optimal water temperature for a swimmer performance? Are there records of swimmer performance vs. water temperature? I'm not a swimmer but in general I would like to understand if there is specific knowledge about this


The viscosity of water decreases with temperature - this means that swimming is quicker in warmer water. As such, FINA regulations require that

Water Temperature shall be 25° - 28°.

(FR 2.12) so that times are comparable between different pools.

  • 3
    But additionally, there's impacts on the body (circulation, nerve response, etc)... so it'd be nice to see real data to see what the complete effect is, and how much it varies by person. Additionally, since the variation within even those 3 degrees is rather significant (3% of the 2°-25° difference), if it has more than a few millisecond impact, it should be a bit factor in times. – JeopardyTempest Jul 18 '16 at 3:49
  • And additionally there's maybe even the added consideration that slight differences in the pool cause big handicaps: 1° is ~2% viscosity difference... if that has the same difference in speed... that'd, for example drop the 2012 gold winner in the 400m (Ryan Lochte) to 4th. There's only so much you can do to perfect conditions, but it'd be interesting to know what impact a degree might really have on a racer! – JeopardyTempest Jul 18 '16 at 9:41
  • Obviously the viscosity decrease reverses severely as you get close to 0 C/32 F. :D – PoloHoleSet Sep 1 '17 at 16:40
  • While the stated temperature limit is true (similar wording in USA Swimming regulations), a direct causal connection to viscosity of the water may not be warranted. As an added data point, the open water rules are, not surprisingly, broader, with a minimum of 16C, and for 5K and longer a maximum of 29.45C, and then further limits on (air+water) temperatures (USA Swimming 702.2). These rules are for athlete safety, particularly after Fran Crippen died in an open water event. – Jon Custer Sep 1 '17 at 18:57

I can not comment. Otherwise I would have and most of my answer may be regarded as opinion based.

My children are/were competition swimmers (almost national level) and have the following observations.

  • Water is too cold, their muscles can not perform.
  • Water is too warm, they can not sweat out their heat (yes, even in water your body transpires heat out!) and this affects performance.

So, it's more a range of temperatures to fit optimal performance ranges. I doubt that it would affect record times as much as being noticeable. Obviously, each athlete has their own optimal temperature range. This would hold for any sport. Having said that, the shorter distances would be expected to have a positive effect of higher water temperatures as you would be able to absorb the heat. Longer distances may even suffer from high temperatures as you can not dissolve the heat.

The regulations (as linked to in another answer) do not state why the temperature needs to be in a specific range. It can not be determined if this is due to less resistance in warmer water or due to the effect of water temperature on bodily performance.

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