Originally Posted by
cyccommute
First, air temperature is just a critical as ground temperature in the formation of ice. Seldom will the ground be cold enough to form ice if the air blanketing it is above the freezing point of water...mostly because the water in the air is above the freezing point of water. Any water deposited on a cold surface is going to give up its heat to the surface warming the very top layers enough that surface where freezing can occur will quickly warm above the freezing point.
The ground being cold enough to freeze water while the air temperature is above (sometimes well above) freezing is a regular occurrence in the midwest, the upper great plains, and the northeast. Maybe that's not how the weather is where you are, but it happens a lot elsewhere. Condensation isn't an issue, because the dew point can stay well below freezing even when the air temperature is 50F.