Maybe I am too simple minded, but icing occurs at the wings of my flown aircraft mainly due to the abundance of water vapor. Temperature is secondary and only relevant for two things, how much water can be carried max in the atmosphere at a given temperature and what is the dew point temperature. Max vapor content of water in atmosphere goes exponential with temperature, so below a certain temperature there is no water in air anyways. Critical is the temperature area where there is enough amount of water vapor possible and physical effects can cause stickiness to the aircraft.