A brief guide to water temperatures in open water

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Temperature Technical term Description
0 to 5 degrees Bloody freezing The preferred temperature for extreme winter swimmers. Causes pain and takes your breath away. Except for the very experienced, and only under strict supervision, swims should be limited to a few minutes. Enjoy the buzz when you get out.
5 to 10 degrees Effing cold Typical lake and river temperature in early spring. Still painfully cold and not recommended for anything other than very short swims (5 to 10 minutes) unless you are very experienced.
10 to 15 degrees Nippy or ‘not as warm as we like it’ Open water starts reaching these temperatures in late spring around much of the UK. At the lower ends, it will still feel extremely cold initially but longer swims are now possible. Experienced swimmers can manage several hours or more as the water approaches the mid teens but hypothermia is still a big risk.
15 to 20 degrees Alright (once you get used to it) The English Channel in summer. If you’ve only ever swum in a pool, this will feel cold but with a bit of experience and practice most people find this range comfortable, at least initially.
20 to 25 degrees Balmy Rarely reached in the sea around the UK, but sometimes in inland lakes. If you’re a habitual wetsuit wearer then seriously consider removing it at these temperatures to avoid overheating. Very pleasant.
25 to 30 degrees Stifling Like a swimming pool. Some open water swimmers find these temperatures too high for serious swimming. Make sure you have plenty to drink. Don't wear a wetsuit.
30 degrees plus Hot Avoid strenuous swimming as there is a definite risk of heat stroke.

Note, swimmers have widely differing opinions about comfortable water temperatures and people’s bodies respond differently. Learn to trust your own experience and feelings.

01 Cover July 21

Issue 51 July 2021

  • Linford Christie on his new interest in outdoor swimming and the secrets behind his success
  • The Icebreakers, a group using cold water swimming to support men's mental health
  • Triple-amputee and former Royal Marine Mark Ormrod on completing a 1km sea swim and inspiring others
  • James Pittar, the first blind swimmer to complete the Triple Crown of Open Water Swimming
  • The frontline workers finding solace in outdoor swimming France’s hidden wild swim spots
  • The revolution in women’s swimwear

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