The temperature of the atmosphere varies with altitude.
At high altitudes (several thousand kilometres) it is extremely hot (about 1000°C).
At intermediate altitudes the atmosphere can be as cold as -100°C.
Near ground level the temperature is on average about 20°C.
Local maxima and minima in atmospheric temperature are used to define boundaries, known as pauses.
The regions between the pauses are labelled using the ending -sphere.
The names of the various regions (working down towards ground level) can be remembered using the memory aid
"The Mess in St Tropez" (Thermosphere, Mesosphere, Stratosphere, Troposphere).
The upper boundary of the thermosphere (the thermopause) is at about 800 km above ground level.
Working down towards ground level the approximate location of the other pauses are 90 km, 60 km and 15 km.
The exact altitudes of the boundaries between the various atmospheric layers vary with the time of day, the time of year and prevailing weather conditions.
Working down towards ground level the approximate temperatures at the four pauses are 1000°C, -100°C, 0°C and 20°C.