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Daryl Ritchison, WDAY, Published June 24 2013

Weather Talk: Rapid evaporation, heat loss behind chilly exit from pool

On a recent sunny day with temperatures in the low 80s, my kids were very surprised by how cold they felt when they were swimming, especially when they were exiting the pool.

You generally feel cold after your morning shower to some degree because you are moving from a warm shower stall to a cooler environment, but mostly from the process of evaporative cooling. The moisture on your skin evaporates, taking energy (heat) away from you, lowering the temperature of your skin. In the case of my children coming out of a pool, even though the air temperature was warmer than your average bathroom, and even with the sun’s radiation helping to warm them up, they were cold.

The dew point was only 40 degrees, meaning the air was very dry. The lower the dew point, the lower the relative humidity, and that, in turn, accelerated the evaporation process. It was this rapid evaporation and corresponding heat loss that made my kids feel exceptionally chilled that particular day, even with temperatures in the lower 80s.


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