I know this title sounds crazy but I don’t know how to phrase my question better
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The feels-like temperature is derived by taking into account the wind speed and humidity. A living body constantly produces heat and sweats to maintain an ideal internal temperature. Wind cools the body down to the temperature of surrounding air by removing warmer air around its surface. Humidity impedes heat loss through evaporation.
A thermometer does not generate heat internally. Once it has reached the temperature of the environment, it will not cool down further as a fresh mass of air moves across it. It is possible to measure the effect of humidity by surrounding the thermometer with a material soaked in water. Then it will cool down below the temperature of the air until the water has evaporated.
“Feels like” corrects for the effects of wind carrying away your body heat, moisture affecting the feel of air, and a few other factors.
But to a thermometer, it isn’t trying to stay warm, and it doesn’t breathe.
Simply, the “feels like” really only applies to living things (and even that isn’t quite accurate).
Let’s say that the air temperature is physically at 40F. At this temperature, water won’t freeze, so your pipes are safe and the roads won’t be icy. If the wind’s not blowing, it’ll feel like 40F.
However, if there’s a 20 mph wind, that will cool you a lot more than no wind. So the “feels like” temperature accounts for this; maybe it’ll say that it feels like 30F. That means that 40F with 20 mph wind will cool you down the same way that 30F air with no wind would. Again, the temperature is still 40F; your pipes are safe and driving isn’t a hassle, but you probably want a thicker coat or jacket.
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Your nerve cells can’t directly sense temperature. Your nerves are sensing “heat flux” and your brain is interpreting it. Basically, it can tell “is heat flowing into my skin, or away from my skin?” and “how quickly is that heat flowing?”
Wind speed and humidity are two things that directly impact how quickly that heat flows. More wind means more air molecules are hitting your skin and transferring heat away from you more quickly. When it gets hot, you sweat and the evaporation of your sweat cools you down. The higher the humidity, the more slowly the sweat evaporates which means that the heat is transferring away from you more slowly.
Wind doesn’t effect the thermometer, because the thermometer gets to the same temperature as the surrounding air. All the wind in the world can hit it, but because they both are at the same temperature, no heat is getting transferred either way.
To give you the “feels like” temperature when it’s cold, they just measure the temperature, and measure the average wind speed, then look it up in a table that some scientists figured out back in the day.
Similarly, to give you the “feels like” temperature when it’s warm, you take the temperature and relative humidity, then look it up in a table.
The temperature is how cold your skin can get. The “feels like” temperature is how fast it gets there.
If the air is 10 degrees and your skin is 20 degrees, over time your skin temp will equalize with the air temp. If the air is still 10 degrees but your skin is 5 degrees, then it will warm up to 10 degrees.
As a lot of factors can go into the “feels like” or wind chill temp, it helps to have a single number for comparison. Heat leaves your skin at a given rate for a given air temp. (The math is fun, but this is ELI5) Colder temps suck out heat faster. So, if the air is 5 degrees but there’s a stiff breeze, your skin will loose heat at a faster rate, like it was 0 degrees.
The cool (hah!) bit is that if it’s 0 degrees but feels like -10 and you have windproof clothing then you only need to insulate yourself to 0 degrees, not tp -10. The windproof clothing prevents the wind from carrying away your precious body heat.
So here’s a fun semi related fact, but we can’t sense moisture. So liquids being wet for example. We just feel the temperature and pressure difference as well as the contact. So you can ‘feel’ it’s wet but really you’re just feeling how everything else has changed.
In a similar way, the thermometer only cares about the temperature. When you have wind, air pressures and moisture content to come into effect these translate a little into temperature feeling too, as well as things like the pressure.
Wind chill is what the temp “feels” like. Thermometers and other inanimate objects, do not “feel”.
*Temp* is you standing in a room, *feels like temp* is standing in front of a fan in the same room.
Inanimate objects are always at the actual temp. The feels like temp is what it feels like to a person who needs to create body heat to stay warm. So in no wind, your body has a thin layer of heat keeping it warm. In wind, that layer gets blown away, so you feel a lot colder.
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