National Center for Cold Water Safety
What is Cold Water
You should treat any water temperature below 70F with caution.
Most people don't think 50F (10C) water is dangerous because they're mentally comparing it to 50F (10C) air. It's an easy mistake to make and it gets a lot of people killed each year.
Water between 50-60F (10-15.5C) can kill you in less than a minute. It's actually so dangerous that it kills a lot of people within seconds. Thousands of people have drowned after falling into cold water and a lot of them died before they even had a chance to reach the surface.
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That's a scientific and medical fact that most people have trouble understanding - because they have no personal experience being in really cold water.
Interesting Facts About Water Temperatures
Important Temperatures
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98.6F (37C) Normal body temperature measured with an oral thermometer.
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99.6F (37.5C) Core temperature of your body.
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95F (35C) Medical definition of hypothermia.
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91F (32.7C) Your skin temperature.
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85F (29.4C) Water feels pleasantly cool.
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77-82F (25-28C) Pool temperature range for Olympic swimming competition.
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70F (21C) Water feels quite cold to most people.
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50-60F (10-15.5C) Maximum Intensity cold shock range.
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40F (4.4C) Water is painfully cold.
Water Temperature Safety Guide
Below 77F (25C)
Breathing begins to be affected.
This is why the official water temperature required for Olympic swimming competition is 77-82F (25-28C).
60-70F (15-21C) Dangerous
Controlling your breathing and holding your breath becomes progressively more difficult as water temperature falls as water temperature falls from 70°F to 60°F (21°C to 15°C).
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50-60F (10-15C)
Very Dangerous/Immediately Life-threatening
Total loss of breathing control. Maximum intensity cold shock. Unable to control gasping and hyperventilation.
Most people who are unaccustomed to cold water will experience a maximum cold shock response somewhere between 50-60F (10-15C). For some individuals, this happens at 57F (14C), for others, the peak occurs at 52F (11C) and so on.
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This means that an unprotected immersion in this temperature range will cause most people to completely lose control of their breathing – they will be gasping and hyperventilating as hard and fast as they can.
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Since cold shock reaches its maximum intensity between 50-60F (10-15C), it can’t get any more intense at lower water temperatures. In other words, breathing control, once completely lost, cannot be lost to a greater degree.
Below 40F (5C)
Very Dangerous/Immediately Life-threatening
Total loss of breathing control. Maximum intensity cold shock. Unable to control gasping and hyperventilation.
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Below 40F (4.5C), water is so painfully cold that it often feels like it’s burning your skin. For many people, the notorious “ice cream headache” can be triggered simply by water touching your face.
Even though cold shock is no more intense than it was between 50-60F (10-15C), the severe pain makes a desperate situation even worse because it greatly increases your psychological stress. Clear thinking becomes almost impossible.
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See for Yourself
If you're in good physical shape and feeling adventurous, a very memorable way to find out about cold water is by conducting a personal experiment.
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Wear whatever clothes you were planning on wearing while kayaking.
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Check the water temperature in your house by running a bathroom faucet for a minute or two, then fill a glass and measure the temperature.
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Turn on the cold water in your shower and let it run till it's nice and cold - then hop right in. No shower? No problem. Have a friend spray you with cold water from a garden hose.