A: The number of calories you burn per hour is a function of how economically you run and how fast you run, both of which can be affected by temperature.
In general, you will burn the same number of calories per hour regardless of air temperature unless the temperature affects your economy (how much oxygen you use to maintain a given pace).
For example, if cold weather means wearing more clothing, the extra weight or constriction of the clothes could increase the cost of running, which would hurt your economy. Therefore, you would burn more calories.
The same thing would happen if you ran on uneven or slippery surfaces. Heat could also hamper economy if it means feeling so bad that you start using poor technique.
Of course, if the heat forces you to slow down, you'll cover less distance in an hour. This means that you would actually burn fewer calories per hour in the heat, though you would still be burning about the same per mile.
Just remember: If your running economy is not being affected, you'll burn about the same number of calories in the heat or cold.