Your body, as a warm-blooded animal, tries to keep a constant temperature (around 98°F or 37°C). Thing is, the body is constantly producing more heat (your metabolism at work…) and needs to get rid of the excess. If the air around you is at the same temperature as you are, it is very hard for heat exchange to take place (for you to get cooler as the air gets hotter) and, thus, you overheat a bit and feel warm.
This is why wind makes you feel cooler: it moves the heated air away from your body and brings in new, cooler air, making the exchange more efficient. Evaporation takes heat away as well, hence we sweat to col ourselves down.
You’ve got a lot of good answers, but I’m missing one important factor why 98F isn’t comfortable for you…
Your body temperature is too high!
Okay bear with me, please…
As I’m sure you’ve already read, your body being 98F/37C needs to get rid of that heat, as well. Your organs like to be 37 degrees, and your body is used to it being colder than that, so it heats itself up for your organs.
Now, what happens if the environmental temperature is usually already around 30-40 degrees?
This happens close to the equator, the whole year, even!
Well, then your body heats up much less.
This means someone from Java (right below the equator) has a healthy body temperature of around 36C, while someone from a colder area like Norway has a healthy body temperature of about 37.5 degrees. 1.5 degree may not seem like a big deal, but keep in mind that a 1 degree raise in temperature already means you have a fever!
This is also why my wife, from Southeast Asia, is incredibly cold here in Northwest Europe, and why I couldn’t enter any store in Indonesia during Covid, cause they scanned my body temperature and 37.5C means you’re very sick over there!
The internal temperature is whatever you said. That’s the temperature your guts need to live.
You have a gigantic organ providing insulation between that and the world. It’s called skin. It keeps the heat in and the cold out and can self regulate for the task too. Doesn’t mean your skin won’t be a relatively high temperature but overall, it’s slightly less than your internals. It keeps your internal temperature that way by releasing the same amount of heat that you produce yourself and capture from the outside, and that difference is usually related to how hot or cold is outside. Because see, heat transfers from a hot to a cold object constantly and passively, and the skin has to chase that value according to demand. Your body will release less heat if it’s cold, and way more if it’s hot out (so it feels even hotter than the air).
Funny detail about fans: Fans don’t actually lower temperatures. Moving air, if anything, should increase it. But it works on us and on electronics for the same reason: We are heat emitters. Pushing air away from an electronic device usually means dragging away the hottest air from the hottest object, so it should overall be cooling down. For us, it also has a bit to do with surface humidity, but that’s because of, again, skin.
I was in the carribean recently and OMG with that humidity an 85 degree day was the worst heat I can recall. I live somewhere that it reaches 100 in the summers. But it’s dry here. And that makes so much difference.
It really made me wonder about my dog, who cannot sweat. Is he dying on an 85 degree day?
I’ve often wondered about our furred friends. Don’t dogs and cats have an internal temp around 101°F (39°C)? That is what searching tells me. I’d think it’s a function of the fur but I’m not sure how it works per cooling.
Google says you’re right. I guess that would make them a little more heat tolerant than we are. I knew they were a few degrees off and that reduces the number of viruses we can share, because most of them are tuned to very specific host body conditions.
Another reason a fan works is because it increases evaporation of sweat. Evaporation involves a phase change which requires energy. That energy is extracted from the body surface. Without air flow the envelope of air next to the skin gets saturated meaning it can’t hold any more water vapor, so evaporation stops.
This differential is critical to managing our core temperature, which is maintained by putting in more energy (running hot) and allowing processes (sweating, capillary dilation in the skin,) to cool off.
This is much more consistent and allows us to inhabit a much greater array of environments than things that are cold blooded.
Not really. Hot Water is relaxing because being warm is relaxing- it loosens muscles and tendons and ligaments while also increasing blood flow (in an attempt to cool off, but it helps with sore muscles by accelerating built up waste,)
But because sweating doesn’t work in a, eventually you’ll over heat and die… eventually. 20min @100 is all it can take.
78f water on a 78f day will feel cooler because of the of the thermal properties of air and water (and sweating,) but that’s not why a hot tub or sauna is relaxing
Your body is generating heat constantly. It’s also attempting to keep the amount of heat created and the amount of heat lost about the same.
As long as the temperature outside is significantly lower than your body’s temperature, it’s pretty easy. Until it gets too cold at least.
When the temperature outside is close to your body temperature, then losing excess heat becomes more difficult. The higher the temperature climbs the more work your body has to do to shed excess heat, and at a certain temperature & humidity, losing excess heat becomes impossible through natural means alone. As it happens that temperature is pretty close to your body temperature at a certain humidity level.
Your body is constantly generating heat. If that heat has nowhere to go, your temperature goes up and up.
You need to be in an environment that sucks heat away as fast as you create it - and if the external air temp isn’t cold enough to do that on its own, then you have to rely on evaporation of sweat to help shed the heat.
It’s the feature that let us become the dominant predator. We could track large game that is wounded until the collapsed from heat exhaustion. Yay sweaty humans!
It also seems like this is part of why there were so many powerhouses around the mediterranean, the climate there is just right that you can work a lot without melting, and warm enough that it’s comfortable to walk basically naked.
And it makes sense when you consider that humans evolved for a comparatively sedate lifestyle (even hunting isn’t going to involve sprinting that much) in subsaharan africa.
So are you saying that people who sweat more in hot environments are better suited for long distance hunting? Because I’m a gross, sweaty mofo and I would like to feel better about it
Probably not I’m sorry. Sweating enough so that the sweat evaporates as fast as it excretes from your pores is optimal. Skin being more wet doesn’t cool faster (drops of sweat falling off you don’t cool you), so excess sweat would just dehydrate you faster. Sorry
I think it has to do with the fact that we are 98° because we create that heat as a by product of living, and there has to be a way for that created heat to be released and moderated.
The hotter it is outside, the harder it is to keep your body cool and prevent overheating. When it's cold, your body has to make more heat energy to keep itself from freezing or slowing down so much you can't operate.
Your body needs to release that heat or risk overheating (heat stroke). If the outside temp is the same as the inside, then you have to rely 100% on sweating. So you’ll feel hot due to the slowing release of heat energy.
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