Lapse Rate and Inversions
The higher one travels into the troposphere, or the first layer of the atmosphere, the lower the temperature becomes. The rate at which the temperature drops is known as the lapse rate. On average, the lapse rate of the troposphere is 3.6 degrees per 1,000 feet, or 6.5 degrees celsius for every 1,000 meters.
This means that for every 1,000 feet that one climbs into the atmosphere, you can expect the average temperature to drop by 3.6 degrees.
Occasionally the normal lapse rate of the troposphere, or lower layer of the atmosphere, can be disrupted or even inverted. In these cases, instead of becoming cooler with increased altitude, the atmosphere becomes warmer with increased altitude.