I’ve noticed that 32°C on a dry day feels way more tolerable than 32°C on a humid day.
Why does humidity make the heat feel worse, even when the actual temperature doesn’t change?
Is it just about sweat not evaporating, or is there more going on in the body or the air?
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Your sweat doesn’t evaporate as well, so it’s harder to cool off.
More water in the air > slower evaporation of sweat > slower cooling down
u/FistoftheSouthStar and u/ImUnderYourBedDude are correct, of course. But then, why does it feel colder when it is cold and humid vice cold and dry?
The drier the air the more “room” it has to store water AND the faster water can move to the air. The more wet the air gets the less room there is to store water AND the slower the water can move to the air. So your sweat evaporates slower, pulls heat off your body slower and then makes your body compensates by sweating more since it’s not cooling down as much as it wants. This more or less makes a humid environment more demanding on the body in hot weather. You can’t just shade from the sun and cool like in a drier environment and you will potentially need even more water than working in the desert at similar temps because your body is not cooling as efficiently so it must sweat more.
Metal at 70*F feels colder than plastic at 70*F. This is because metal conducts heats better, therefore it’s “colder” in the sense of, heat leaves your fingers faster. Even though both are the same temperature.
In 100% humidity, you are touching air that’s more like the plastic.
Human bodies are constantly producing heat that needs to go somewhere. The sensation of that heat leaving your body fast or slow is the cool or hot feeling, not just the temperature.
water is an insulator and humidity tells you how much water is in the air (water is a insulator but can have conductors in it making it conductive but water itself is an insulator and water vapor is pure water)
The “cooling system” of our bodies is based on evaporation of sweat.
Evaporation (the transition from liquid to gas phase) requires energy, therefore this process extracts thermal energy from our body which cools it down.
The more water vapor the air contains already, the slower the evaporation process gets and the worse our “cooling system” performs. Therefore moist air “feels hotter” than dry air of the same temperature.
When relative humidity reaches 100%, the air is completely saturated with water and sweat will no longer evaporate at all.
Because the more water vapor already in the air, the less your perspiration evaporates away into the air. The air at a given temperature can only hold so much water vapor. Evaporating perspiration is what cools you off.
Sweat doesn’t evaporate when humidity is high. When we moved to Arizona with its 5% humidity, I was surprised I didn’t seem to be sweating. But when I took my tee shirt off, it was stiff with salts from dried sweat.
What we feel as “temperature” is more or less an approximation. What we we’re good at feeling is heat transfer.
A piece of metal and a piece of cotton can be at the same temp, but metal will feel cooler because it draws heat from our skin faster because metal is a better conductor.
We feel heat transfer and our brain approximates it as temperature. It’s a good measure… Most of the time but it’s not perfect.
Drier air and humid air can change how fast heat transfers from our bodies, so it can sometimes feel like different temperatures.
It’s just about the sweat not evaporating. Air can only hold so much moisture, so when it’s humid it is harder to get sweat to evaporate. Evaporation requires heat energy to accomplish, that is how it cools you. No evaporation and you are a hot sweaty mess.
I need the question restated in Freedom Units to answer