When is carburetor icing most likely to form?

Carburetor icing is most likely to occur when the air temperature is between -7 °C and 21 °C with humidity present due to the cooling effect caused by the vaporization of fuel in the carburetor. As fuel is drawn through the carburetor, it absorbs heat from its surroundings, leading to a temperature drop that can create the conditions necessary for ice formation. The presence of moisture in the air can further facilitate this process since water vapor condenses and freezes when temperatures are low enough.

Icing concerns significantly lessen at temperatures above 21 °C, as warmer air does not foster the same cooling conditions necessary for ice to form in the carburetor. Additionally, when temperatures drop below -7 °C, although icing is possible, the formation mechanisms and effectiveness are different than at temperatures just above freezing due to other factors like engine operation and fuel properties. Flying in dry, cold air also tends to reduce the risk of carburetor icing since the lack of humidity limits the amount of moisture available to freeze within the carburetor. Thus, the primary risk is concentrated in that specific range of temperatures with sufficient humidity.