What makes “felt” temperature differs from real temperature in weather forecast?


What I mean is [like this](https://imgur.com/a/jQ867F3)

In: Physics

Usually wind and humidity. Those two affect how humans perceive temperature, but don’t actually change the real temperature

It may not be entirely because of this, but I believe it’s because of humidity and wind speed. High humidity means less heat is being taken away from your body by evaporation, and lower wind speed similarly means less heat is being pulled away from your body, but I’m not sure if those are the only/relevant factors.

The felt temperature is called the heat index if I’m not mistaken.

The place I live is like when it is +30 it is felt like +44, and when it is -5 it’s felt like -20. Depending on many factors such as whether or not it’s cloudy, wind speed, humidity, exterior etc.

What humans perceive as cold is really just the rate of energy escaping from our bodies. There are several things that affect how fast something is cooled down, such as humidity and wind.

In hot weather, high humidity prevents your body’s main method of temperature regulation (evaporative cooling by sweating) from working optimally. This method of cooling works because it requires a lot of energy for water to change phases from liquid to gas.

When this process happens, the energy required for the phase change to happen is sucked out of your skin and travels away along with the water vapor. However, this physical process does not happen if the air already has the maximum amount of water vapor it can hold, which will cause your sweat to just build up on your skin and do nothing, instead of evaporating and cooling you down.

In extremely dry regions, humans can survive at much higher temperatures if they just have access to water. It doesn’t even have to be cold water. It is theorized that this is one of the evolutionary drivers that caused us to lose much of our hair. Having big, smooth surfaces of skin for sweat to evaporate from would allow for a great degree of cooling in the warm weather that we evolved in.

The other way we cool down is by heat transfer into whatever is touching our skin. If we touch something that’s very dense, such as metal, it feels cold because that material is conducting heat away from our bodies very rapidly, but eventually it heats up and feels warmer, right? Same happens to the air around us, but the air conducts heat much worse than metal. However, air also moves around more easily than metal, so if there is a slight breeze, the air that was heated by your body is easily blown away and replaced with new air that has not yet been warmed by your body, which causes you to cool down because you’re not losing heat energy to that new bunch of air molecules.

Warm clothes work because they trap air inside the fabric and between the fabric and skin, so that the air you spend energy on heating up doesn’t just disappear when you start moving.