The Sun sets.... so why does it feel hotter overnight?

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SUMMARY

The discussion centers on the perception of increased heat at night despite cooler air temperatures. Key factors include the constant moisture levels in the air, which hinder effective sweating and cooling, and the body's temperature fluctuations throughout the day. Tom emphasizes that while air temperature drops, the sensation of heat may be more about perception than actual temperature differences. He suggests that using a low-speed fan can significantly improve comfort levels during the night.

PREREQUISITES
  • Understanding of thermal comfort principles
  • Knowledge of humidity's impact on body temperature regulation
  • Familiarity with convection cooling methods
  • Basic awareness of air conditioning settings and their effects
NEXT STEPS
  • Research the effects of humidity on thermal comfort
  • Learn about body temperature regulation throughout the day
  • Explore convection cooling techniques for improved sleep comfort
  • Investigate the effectiveness of different fan speeds in cooling environments
USEFUL FOR

This discussion is beneficial for individuals seeking to understand nighttime heat perception, including homeowners, HVAC professionals, and anyone interested in improving sleep comfort through environmental adjustments.

hmmm27
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TL;DR
When I was a kid, nobody had air-conditioning. At the end of a hot, muggy day we'd find it impossible to sleep, drenched in sweat...
I've always wondered why.
Would the reason be that the air cools but the amount of moisture stays the same... which makes sweating less effective... which means no cooling effect even though the air is technically cooler.
 
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It might have something to do with your body temperature increasing over the course of the day. I always have to bump down my AC from 78 to 74 (or less) to stay comfortable in the evenings before I go to bed. But that's pure speculation on my end.

In any case, I'd be willing to bet it's more perception than an actual difference in the air.

hmmm27 said:
Would the reason be that the air cools but the amount of moisture stays the same...
According to wiki:
"Although humidity is an important factor for thermal comfort, humans are more sensitive to variations in temperature than they are to changes in relative humidity."
 
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Just to point out the obvious, a substantial portion of your body is well insulated when in contact with the mattress.

Also convection cooling is inhibited by being so close to the mattress. A low speed fan in the bedroon can help immensly.

Cheers,
Tom
 
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