WeatherTalk: The air is often warmer a few hundred feet up
This layer of air is known meteorologically as the "boundary layer."
The layer of air comprising the lower few hundred feet above the ground is known meteorologically as the "boundary layer." It is this lower layer of the atmosphere that is most affected by the interaction between sunshine and the Earth's surface. In winter, when the ground is covered in snow, a great deal of the warming rays of sunlight are reflected back into space, allowing the boundary layer to get and stay cool.
Temperature inversions, when a layer of warm air aloft covers cooler air below, are much more common during winter. When the boundary layer is particularly cold, it is not unusual to the a large plume of smoke or steam from any sort of large-scale combustion like a factory to reveal a change in direction at some point a few hundred feet up. This change is occurring at the top of the boundary layer. The observer can assume that the temperature of the air above this wind shift is warmer than the air at the ground.