The rate of ice accretion on an aircraft depends upon meteorological factors and aircraft characteristics. There are on the one hand atmospheric pressure and temperature; water content; droplet size; electrostatic conditions. On the other hand, there is the collection efficiency made up of aircraft component design characteristics such as size; shape; material; surface finish. Finally, there are aircraft flight variables such as speed; attitude; skin temperature; vibratory state.

Meteorologists are able to define potential icing intensity if they can forecast the ambient factors mentioned. The intensity may be defined as light, moderate, or severe, or by some such broad adjective, with reference to a hypothetical collector. Similarly, the air-worthiness authority, e.g. the Air Registration Board, must be satisfied that an aircraft can be operated safely in the appropriate meteorological conditions. Therefore the probable association of each meteorological factor with the others needs to be known.