I always related to a damp muggy feeling, where we live it is very dry ,but travel to the coast and the same temp down there feels at least 10 to 15 degrees hotter.

What cools your skin is the perspiration as it evaporates. When water evaporates, it absorbs heat. The higher the humidity, the less evaporation off your skin, the hotter it feels. The lower the humidity, the more rapidly the perspiration evaporates, the cooler you feel.

High humidity increases the air thickness. Think about how cooler the weather is on mountains. The thinner air there decreases the temperature (about 4 degrees for every 1000 feet).
The thicker, humid air also keeps it’s warmth better than thin air.

The water molecules in the air store the heat from the atmosphere like a battery stores energy. Then it compounds the ambient temperature and sustains it longer, giving you the higher “feels like” temp you see on the weather report. That is also why daytime temps in humid environments do not cool much during the night. A 96F daytime temp might reach an 88F low before dawn. Conversely, in a dry environment such as the Mohave Desert, a daytime high of 120F can reach a nighttime low of 48F because there is no water in the air to hold the heat.

Interesting question, looking forward to learning the answer.
All I know is that even when it is only 70 something degrees in asian and tropical climates it feels much hotter because of the humidity.

@Espiritus_Corvus Aaaah, so water molecules retain heat. makes sense.

@kritiper nailed it.

I ♥ you guys. Thanks.

When we perspire we are depending upon the evaporation process to cool us down. That’s why a breeze or a fan will feel cooler. High humidity impedes this because there is already moisture in the air.

One of the adjustments I had to make when I moved to a dryer clime was water intake. Because of the low humidity and high evaporation, one can be perspiring all day long and not realize it because no moisture accumulates on the skin.

Here ws a Heat Index chart from the US Weather Service.

For the same reason a cold ocean fog (like here in San Francisco( makes it feel so much colder. The temperature preservation in the air makes it difficult to make your skin warmer (or cooler) so your body temp goes whacko.

I kinda sorta knew the answer but it took answers in this thread (all of which I lurved, as well as the question) to really explain it for me.

So nice being surrounded my smart people! I really mean that.

Yes @kritiper and @Yetanotheruser nailed it.

@Coloma Yes. That’s why your A/C unit comes with a dehumidifier function. It simultaneously removes water molecules from the air while cooling off the rest. Less water molecules to cool means faster, more efficient, cheaper temp reduction per BTU/M 3.

@zenvelo I dream of those cool, foggy San Francisco nights.

@Espiritus_corvus That’s why your A/C unit comes with a dehumidifier function.

And that’s also why in dryer environs the evaporative or “swamp” cooler works so well. Cool by evaporation _and _ adding humidity to the air.

That’s with a Capital C to you, boy.

Careful who ya call “boy” there, sonny!

^ geezer fight, take out your hearing aides and draw your canes gents. LOL

I nominate @Coloma to be the official geezerette referee!

Geezerette, LOL