Silly meteorological question.

[Biggirl]

If heat rises, why does it get colder as you go up?

Told you it was silly

[Johnny_L.A]

From this site:

DRY ADIABATIC LAPSE RATE.— If a parcel of air is lifted, its pressure is DECREASED, since pressure decreases with height, and its temperature falls due to the expansion. If the air is dry and the process is adiabatic, the rate of temperature fall is 1°C per 100 meters of lift (10°C per Km), or 5 1/2°F per 1,000 feet of lift. If that parcel descends again to higher pressure, its temperature then INCREASES at the rate of 1°C

[Johnny_L.A]

A more detailed explanation is on this site:

As a child, I could never understand why the atmosphere gets colder the higher up you go. I reasoned that as higher altitudes are closer to the sun they ought to be hotter. In fact, the explanation is quite simple. It depends on three important properties of air. The first important property is that air is transparent to most, but by no means all, of the electromagnetic spectrum. In particular, most infrared radiation, which carries heat energy, passes straight through the lower atmosphere and heats the ground. In other words, the lower atmosphere is heated from below, not from above.

[snip]

The basic reason why air is colder at higher altitudes is that it expands as its pressure decreases with height. It, therefore, does work on its environment, without absorbing any heat (because of its low thermal conductivity), so its internal energy, and, hence, its temperature decreases.

[Telemark]

Slight nitpick: Heat doesn’t rise; hot air rises.