Originally Posted by
AlmostTrick
Both. I believe it's a valid question for the reasons I stated.
"Even in hot weather the wind cools our body down, that's why people use fans. That's why we feel cooler on a moving bike than one stopped at a red light."
You are partially correct. This works
in a dry (<30% relative humidity) environment.
The reason is that when liquid evaporates, it is absorbing energy (latent heat of vaporization). We feel that absorption as cooling. Unfortunately, once the humidity gets too high, not enough evaporation goes on, and you just get moist.
Our environmental body temperature (as opposed to our core temperature) is right around 89F. This means at 89F, if you aren't really doing anything, your body's heat output/input would be balanced. However, our bodies are always "doing something"....they are metabolizing and constantly generating heat. That's why our actual comfort zone is much lower.
If you look at the chart I linked to above, it doesn't even start until 40F and colder. The chart assumes a few things: 1) we aren't running around outside naked; 2) we have
some control over how long we are exposed to wind/cold.
An exposed (naked, essentially) human can stand temps down to about 60F indefinitely. It's chilly, but you won't die unless you are exposed for really long (like longer than you would need to die of dehydration or starvation anyway). Above that, and up into about the mid 80s, you're pretty much safe from any kind of temperature related effects unless you're
really exerting yourself.
Once you start getting warmer, you run the risk of overheating, so again, the warnings only start when it gets to the point where it can happen quickly enough that you are reasonably likely to pass out/die before you can get into cover or get cooled off.
Since you have some motorcycling background, here's an interesting tidbit: In the summer, in a dry environment, if you wear light colored leathers or MC specific clothing with some ventilation, you will stay cooler than that the full mesh riding gear that is so popular. I used to ride my CBR in AZ all summer long and I would always wear my leathers. It sucked if I was in traffic, but I generally use that bike for fun rides, and not commuting.
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