The earth's coldest natural temperatures are occurring about sixty miles above your head, where temperatures can get as low as 146 degrees Fahrenheit below zero.
This is the top of the mesosphere – the layer of the earth's atmosphere above the stratosphere. Being too high for aircraft but too low for orbiting spacecraft, the mesosphere is the least-understood part of our atmosphere. The coldest part of the mesosphere is the mesopause, the boundary between the mesosphere and the thermosphere.
Above the mesopause, solar radiation can push temperatures to over 2,700 degrees, although the gas molecules at these altitudes are so far apart that temperature cannot be measured in a conventional sense.
