Perception of heat

Re: Perception of heat


30C is 30C no matter where the temp is taken.

Besides humidity, one factor that affects a person's perception of environmental heat, is the color/pigmentation of their skin. Thus, since pigmentation is determined via both genetics and biochemistry, these two latter factors will also affect one's "perception" of environmental heat.

Many things obviously affect the perception of how it is outside. These things can be broken down into several general categories:

1) The temperature of the environment relative to your body's temperature and what the body is set to interpret as hot. This should be relatively obvious. How "hot" do you feel when you walk from inside an air-conditioned house to the boiling heat of summer? One reason people who live in hot climates still feel comfortable is the adjustment of the body to "like" the hot temperate. Also, think about getting a fever: when you start to get a fever, you usually feel ice cold, regardless of the temperature outside, because the body thinks it needs to be a few degrees hotter.

2) The ability of the environment to heat your body. Skin pigmentation falls into this category, as certain pigment types absorb sunlight more readily. Clothing worn can also reflect or absorb more of the environmental heat. Liquids conduct heat better than gases, so a hot pool might be more uncomforable than the same temperature air. How much heat your own body is producing will of course also contribute to the increase in your body's overall heat level.

3) The ability of your body to keep from heating. Humidity falls into this category. High humidity hinders one of the body's defenses against heating up: sweating. Being acclimated to hot weather (people living in Florida all their lives) will affect the efficiency of sweating, the electrolyte:water ratio in sweat, and the ability of the body to push blood to the skin surface to get rid of heat. Being dehydrated will also impair your sweating ability. You body weight also affects the ability to get rid of heat: skinny people have higher surface area to body volume and thus more area from which to get rid of excess heat. And finally, wind in the environment makes this process more efficient, removing the heat from the skin surface more quickly.

4) Your cognitive/emotional state. Ever play a game of football in the middle of summer and not realize how hot it was outside? Ever realize you've lost your airline luggage and then walked out into a mildly warm sunny day? Try comparing 30 degrees celsius "on your drive to work with no air-conditioning" and "on the beach during the funnest vacation in Italy of your life".

Pedro, that was an immensely useful post. Welcome to a2k.

Wow. You guys are so competent! Thanks.

Pedro interpreted me correctly. I was talking about one person in different climates. The weather websites specify some kind of "real feel" temperature and I wondered how they calculate it.

It just struck me that when I visited Italy, Croatia, Uzbekistan, North China - it was more breathable with roughly the same range of temperatures than back home. My observation was confirmed by other people. I also heard that people in hot Sydney and even hotter and more humid Brisbane and Gold Coast in Australia rarely use air conditioning.

The relevant differences I can think of - it never rains in summer in the Middle East, and maybe spicier food (?) . Maybe it's also the mental state, like being on a vacation :-) .

Galilite, this is all interesting, and people on a2k would be interested in your travel comments too. Hope you folks keep posting.

Thank you . I will.

Great place, by the way - large, multinational and flame-free.

By the way, I forgot to add in "wind" into my original reply, so I added it into my previous post under category #3.


Oh, there is a slightly different answer to this question. Weatherpeople use 2 different indexes to report the "how hot or cold does it feel" temperature. Unfortunately, the 2 scales are not used together. One scale reports how "hot" it feels to someone, this is the heat index. The other scale reports how "cold" it feels to someone, this is the "wind chill factor". You cannot combine the 2 methods for a single overall "how does the temperature feel" index, as far as I know. Many factors about how hot or cold it really feels are left out of these calculations, they only take into account humidity or wind.

So it sounds like you are most interested in the heat index, which is how the weather channels report the "feels like" temperature. It is calculated solely based on actual temperature and humidity. Check out this web site for more information on how to calculate it yourself: http://www.mistupid.com/convert/heatindex.htm

Yes, wind too. This probably explains how people in Queensland manage without air-con.