Someone tells me that on humid days, sweat that makes skin feel sticky or damp is mostly just condensation and not actually sweat. But that sounds like BS, because body temperature is almost always going to be hotter than ambient temperature, so condensation can’t form.
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Correct, we are almost always hotter than the surrounding air and we are actively trying to force water to evaporate.
Generally speaking no, it isn’t condensation (unless you’re like in a steam room – the conditions that would have water condensing out of the air onto your skin would not be tolerable for long).
Yup, we are almost always going to be warmer than ambient. Which means it’s impossible for condensation to form.
The only situation in which it’s possible to form is likely…super deadly. Like…you would die within hours/minutes? (I am really struggling to find exact numbers for this duration)
Because the dew point (the temperature at which water will condese) would have to be above human body temperature. This is a function of both temperature and relative humidity. We often combine those two metric to get the “heat index” (which you have probably heard about either that or the “real feel” is another term for it.
What heat index do we need to realistically get condesation to form on a person? About 86 C (187 F) For context a heat index of 52 C (125 F) is considered an extreme danger.
You’re right. A surface collects condensation when its temperature is below the dew point of the air around it. For example, in 80F (27C) air with 75% humidity, your skin would need to be below 71F (22C) for condensation to even begin to form on it. With the help of something cold you might be able to get the outer layer of your skin below dew point in very warm humid weather, but it wouldn’t last long enough between the heat of your body and the air around you to actually contribute significantly.
Nah. (edit: mostly nah)
On humid days what happens is that your sweat is prevented (not completely, but mostly) from evaporating. That’s why we tend to be moist and sticky while simultaneously being extra hot. *edit: our sweat isn’t evaporating and taking our heat away.*
Body temp is not hotter than ambient temp during summer. At least not here in Texas. But even then it is not cool enough to cause condensation.
Lets say you weren’t sweating at all, your skin would have to be colder than the dew point for water to condense on it. In this scenario you’d die very quickly because you would be unable to cool off, you’d basically be steaming yourself.
When you get wet with sweat, it’s because the air cannot absorb the water faster than you’re secreting it. Once the air absorbs the water it can carry, you need to move it away from your skin and replace it with drier air. This process is much easier when there’s low humidity and some wind.
Technically, there’s transfer of water molecules both ways across the air-liquid boundary, but there’s more water evaporating than condensing.
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