If temperature is a measure of how fast particles move, why wind isn’t making the temperature higher?


If I understand correctly, temperature is a measure of the kinetic energy of particles which corresponds to how fast they move. But if that’s the case, why is the air temperature in winds not higher, since it pushes particles faster?

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It does make materials warmer, but not enough to matter, and thanks to other properties can also make things cooler.

Temperature is about motion at a molecular/atomic scale. It’s about really tiny movements.

Wind is motion at a much larger scale than temperature. The motion of wind causes turbulence which results in a tiny amount of friction warming, but it has other effects. For humans it carries away the air around your body, allowing for more evaporation (which usually cools) and takes away whatever air your body has already warmed. Both of these drop your temperature around your skin.

Overall wind by itself has a negligible effect on temperature. If same-temperature air is moving through same-temperature air, the air remains at the same temperature. However, usually wind moves from high pressure to low pressure, and pressure differences are often due to temperature differences, so you get either colder air moving through or warmer air moving through, which is just replacing air with different temperature air.

The easiest way to see why we don’t feel the wind as being noticeably hotter is to compare how fast the wind moves to how fast the gas molecules that make up the wind move due to their temperature. A nice, brisk wind is going to be ~10 m/s. The thermal motion of air molecules at around room temperature is ~500 m/s, so that additional 10 m/s is very small compared to the speeds at which the particles are moving randomly due to their temperature. Imagine a bullet train going by you at 150 mph. Someone walking down the aisle of the train is not moving at the exact same speed as the train, but from your perspective from the outside, they’re moving at almost the same speed by you as someone who is seated on the train. The 2% difference in their speed compared to the seated passenger’s speed relative to you is very small.

You have to be going like 1,000 mph before the heating due to wind gets really significant (and, sure enough, supersonic aircraft do get pretty hot when they’re moving through the air at speeds over Mach 1). For low wind speeds, the wind often has a cooling effect, as body temperature is usually higher than the temperature of the air and even above that we cool ourselves by evaporating sweat, so having a constant supply of cooler and/or dryer air lets us cool off more effectively.

There are some additional complications, though these fall outside of what we would consider ELI5, for the most part:

First, temperature is defined where the *average* motion of all the particles in the system is zero, or in other words the motion that we take into account when talking about temperature of wind is the motion we would measure if we were moving along with the wind. The wind’s macroscopic motion itself is called “bulk motion” and is a different phenomena. So when we talk about the temperature of the air, we don’t say it’s different when we are standing still in it vs. when we are flying through it at supersonic speeds, because in both cases we measure the temperature from where we are standing still in the air. In the supersonic case, we say that there is additional *heating* due to the relative, bulk motion of the air.

Lastly, temperature is not just a measure of the kinetic energy of the particles of a system, though for gasses at room temperature that’s a good enough approximation and works just fine for the context of your question.

Friction from the wind can make things warmer.

BUT, wind feels colder to humans, why? Because we generate heat.

Right, so you are constantly dumping heat into the air around us, and in a still day with no wind, we actually heat up a little bubble of air around us, making us feel warmer.

But wind blows that bubble away, introducing new colder air, making us feel colder.

So wind makes things feel colder because it increases how fast that thing loses heat