The mesosphere is the coldest atmospheric layer surrounding the earth. It becomes cold enough to freeze water vapour in its atmosphere into ice clouds. These ice clouds are blue-white and are called noctilucent clouds or polar mesospheric clouds. These clouds are more visible at sunset from the earth’s poles.
What is the average temperature in the mesosphere?
The top of the mesosphere is the coldest part of the atmosphere. It can get down to -90° C (-130° F) there! As you go higher in the mesosphere, the air gets colder. The air is much thinner (less dense) in the mesosphere than in the stratosphere below.