– How does concrete/asphalt heat up to insane temperatures that are way above the actual air temperature?


The question pretty much sums it up. How TF is the asphalt 20-40° hotter than the air when it’s super hot?

In: 531

Concrete (and more especially asphalt because of its darker color) absorbs light and heat from the sun, unlike the air which lets radiation pass through it.

Heat can only transfer to the surrounding air so quickly, and on really hot days the sun just outpaces it. Concrete can store a lot of heat, and it gets hot from the sun faster than the air around it can wick the heat away.

The first thing to understand is that it isn’t the air that’s heating the concrete, it’s the sun.

Sunlight does heat the air, but for the most part sunlight just passes through the air and hits the ground

Concrete is just very efficient at absorbing heat compared to air, so when it gets baked by the sun all day it can get up to very high temperatures.

A lot of the ambient air temperature actually comes from radiant heat coming from the ground interacting with the air, not from the sun heating the air. This is in part why it gets colder at higher altitudes despite the sun hitting that air first. There’s less radiant heat from the ground heating the air up there, that and the air is thinner.

When nightfall hits it isn’t the air temperature that keeps the planet warm, it’s the radiant heat coming off everything else. The ground, buildings, trees, etc..

The concrete and the air are both being warmed by radiation from the sun.

When sun radiation hits a solid dark object like asphalt, the light is absorbed by the surface and converted into heat (heat is just how fast an object’s atoms are wiggling. The incoming light knocks into them and they wiggle more).

Air, being transparent, lets a lot of this radiation pass through rather than absorbing it and converting it to heat. So the air doesn’t warm up as much.

The ground surface is heated by the sun rather than by the air. In fact, the air is heated primarily by the ground rather than by the sun itself. In the absence of air, the ground would actually be considerably hotter.