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Ninjaromeo t1_j0l4o14 wrote

Reply to comment by [deleted] in How does high humidity affect perceived temperature in hot and cold environments? by MindTheReddit

Funny. I didn't think much about it for hot climates. When it is cold and you are wet, you definitely feel more cold.

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[deleted] t1_j0l6ffl wrote

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m31td0wn t1_j0l8gl9 wrote

That's just evaporative cooling, same as sweating. Although it is possible to cool the air by increasing relative humidity--that's how "swamp coolers" work. Basically humidifiers that spray a fine mist of water into the air, which in extremely arid environments evaporates quickly and lowers air temperature by raising relative humidity. It takes energy for water to phase shift from a liquid to a gas, and that energy comes directly out of the air it evaporates into.

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[deleted] t1_j0lhpn1 wrote

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m31td0wn t1_j0lo7hj wrote

Haha well temperature is just kinetic energy of molecules. Picture the atmosphere as a giant bag of marbles being shaken around. The faster it's being shaken, the more heat it contains. But if you add more marbles to the air, it becomes heavier, and harder to shake. So the shaking slows down. Keep adding more marbles, it's heavier and heavier, so it gets shaken slower and slower.

Not a perfect analogy but I think it gets the job done. The energy required to turn water into a gas is drawn out of the air, causing the air to lower in temperature.

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kilotesla t1_j0lvkj4 wrote

I think a better (but still sloppy and qualitative) analogy is that if the marbles bouncing around hit a layer of stationary marbles held together with pudding, and they knock loose some more marbles when they hit, that process will absorb use up some of their kinetic energy.

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Dani_924 t1_j0l8xoa wrote

It’s like being in a steam sauna but you’re outside and can’t escape it. High heat and humidity are brutal. Also see ‘wet bulb effect’. Sweating does absolutely nothing to cool you off. Swimming can help as long as the water is cooler than the air temperature.

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doghouse2001 t1_j0n1auw wrote

Swimming can help as long as water is cooler than your normal body temperature.

If it's 100 degress F and the water is 90 degrees F you'll still overheat and die.

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Dani_924 t1_j0nany9 wrote

Good point. I was thinking of a regular pool or natural body of water, which for the most part are usually cooler than a persons body temperature. I would definitely not recommend swimming in a hot tub during a heat event.

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s0rce t1_j0lgqxm wrote

Then the humidity would make you warmer by reducing evaporative cooling

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Dani_924 t1_j0mesr1 wrote

Yeah that’s exactly what happens. Where I live in Canada, in the summer there is the air temperature, and then there is the ‘humidex value’. So it can be 25 degrees Celsius but with the humidity it will “feel like” 30 degrees Celsius. It gets dangerous when the air temperature is already in the 30 degree range and the humidity makes it feel closer to 40 or higher. Then we get heat warnings for people to be careful because you can get heat stroke pretty easily.

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Ashmedai t1_j0lgqbb wrote

> Funny. I didn't think much about it for hot climates.

Not so fun fact. There is a rare environmental condition that can occur where the heat index around you can go up higher than the body's cooling ability can handle. If you are caught in such an environmental condition and cannot find shelter, you'll die. No amount of water will help, as sweating cannot cool you.

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kilotesla t1_j0lb1tj wrote

When you are wet is a little different from the air having high humidity. If you are wet, evaporative cooling has an impact, and if your clothes are wet, their insulation capability is degraded.

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