At what temperature does hot air start to fall?

Question

what temperature does air start to fall at? when its hot it rises, so how cold does it need to get before falling?

Answer 1

Hot air rises and cool air moves in to take its place.
(The rising air is called a 'Thermal')

The rising and falling circulation is somewhat in the shape of a mushroom.

When the upper volume of rising air cools sufficiently below its initial temperature it returns to the base of the rising column.

(Convection currents)

Answer 2

As you rightly mentioned, hot air rises because it is lighter than the surrounding air. When it rises, it expands and cools. Also, the surrounding air is also getting cooler since the distance from the heat source, which is the earth surface is increasing. However, local differences in air temperature cause air turbulence and allow for mixing of air. These air streams do descend to the lower altitudes just like ocean currents. It is a complex model.

Answer 3

Hot air does not actually "rise", it is pushed upwards by colder air entering from underneath. Unless that hot air is lost up above, which often happens, it may well cool and be drawn back down into the equation again as the cooler air below warms and is pushed upwards itself.

Answer 4

it just needs to get colder than the air below it, then it starts to fall.

Answer 5

DOH!!