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[Phys-l] it's a dry heat



On 07/26/2011 09:43 AM, Paul Nord wrote:
Does any of us have the experience to know what 98º would feel like
WITHOUT the local humidity common to your area?

Some of us do.

I grew up in the high desert. Consider a typical June day. Officially
it is 110 F in the shade, but there's no shade. It hasn't rained in
a couple of months, and there is zero chance that it will rain in the
next several weeks. The relative humidity is 5 percent. That corresponds
to a dewpoint of 24 F ... but actually that's not a dew point, it's a
frost point, because it is below freezing. You can leave a glass of
icewater sitting outside and it will not collect condensation. In fact
if there is initially water on the outside of the glass, it will evaporate.

I know exactly what that feels like. It's not bad ... if you have enough
water. Imagine going for a bike ride, 9 miles in 40 minutes, with an
elevation gain of 400 feet at one point. That's an average of more than
13 mph. If you drink as much as you can before setting out, and drink
two liters of water along the way, you will be thirsty when you get back.
It's definitely hot, but it's not uncomfortable, and you can exercise
all you want ... if you have plenty of water.

This stands in contrast to situations with high humidity and lower
temperatures, where it is uncomfortable just sitting around, and
exercise is out of the question.