The mesosphere (; from Greek mesos "middle" and sphaira "ball") is the layer of the Earth's atmosphere that is directly above the stratopause and directly below the mesopause. In the mesosphere temperature decreases as the altitude increases. The upper boundary of the mesosphere is the mesopause, which can be the coldest naturally occurring place on Earth with temperatures below . The exact upper and lower boundaries of the mesosphere vary with latitude and with season, but the lower boundary of the mesosphere is usually located at heights of about above the Earth's surface and the mesopause is usually at heights near , except at middle and high latitudes in summer where it descends to heights of about .