For example right now it is 30C degrees but because of the humidity it “feels like” 36C. Why does more humidity in the air increase the temperature?
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When a liquid evaporates, the “hotter” molecules are the first to turn into gas and escape. This means average temperature of the liquid is cooler than before, since the hottest molecules leave and the coolest molecules remain.
When the air is humid, it’s harder for sweat to evaporate. So you get less of a cooling effect than you get when the air is not humid.
A big aspect of this is just the fact that air is not a good conductor, but water is. So if humidity is high, a hot day might feel hotter on your skin, and a cold day might feel colder. That’s just because the higher concentration of H2O molecules in the air are better at conducting the temperature to your skin.
Humidity can be reported as *absolute humidity* measured as mass of water vapor per volume of air, or the commonly used *relative humidity* measured as a percentage of water vapor in air out of the maximum possible *at that temperature*.
Heat indexes from the weather use relative humidity to report a higher temperature *aka – feels like XX°F* because as relative humidity goes up, evaporation rate of water goes down*(this has to do with vapor pressures and I dont know how to ELI5 for that)*. When evaporation rate goes down, your body cannot shed heat as quickly via sweat evaporation. This is why 110°F @ 5%Rh in the desert *feels* as comfortable as 70°F @ 80%Rh in a place like southeast US. You can actually compare conditions using a [wet bulb calculator](https://www.omnicalculator.com/physics/wet-bulb) though you may want to understand the difference between wet and dry bulb temperatures first.
Anyone please, correct me if I am wrong.
Humidity doesn’t change temperature. Temperature changes humidity.
There is water vapour in air. Consider a certain volume of air(say one cubic meter) at a certain temperature, say 30°C. Let’s assume, 40 g of water vapour is present in this air volume. Now, if decrease the temperature, say, to 25°C, we would see liquid water forming.
This happens because, there is a certain amount of water vapour a certain volume of air can hold at a certain temperature. Keeping the air volume constant, and increasing temperature will increase the vapour amount that can be held, and decreasing temperature will decrease the amount of vapour that can be held, in that particular volume of air. So above, decreasing temperature decreased the amount of water vapour that can be held, say at 25°C can hold only 30 g of water vapour, so there is an additional 10g of vapour that will have to condense, forming water, and provide space for the remaining vapour.
Humidity is the proportion of water vapour in one cubic meter of air at the moment and temperature considered to the maximum amount of water vapour one cubic meter of air can hold at that considered temperature, given in percentage. There are a few other definitions but this is the easiest one to wrap my head around.
So as nature goes, let’s consider the air volume to be constant(that’s a safe assumption). So at 30°C, you feel like its 36°C because water vapour content has increased in the air, almost to the maximum level that can be reached at 30°C, thus increasing humidity to almost 100%.
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