Which type of precipitation is most hazardous to aviation?

Freezing rain is particularly hazardous to aviation due to the way it forms and its effects on aircraft. When rain falls through a layer of cold air, it can become supercooled, meaning it remains in liquid form even below freezing temperatures. Upon contact with any surface, including aircraft wings and windshields, this supercooled liquid instantly freezes, creating a thin layer of ice.

Ice accumulation on aircraft can severely disrupt aerodynamics, increase weight, and affect aircraft control surfaces, leading to a higher risk of accidents during takeoff, flight, and landing. Additionally, it can impede visibility for pilots when ice forms on the windshield.

In contrast, while snow can also impact visibility and runway conditions, it typically doesn't adhere to aircraft in the same way that freezing rain does. Rain can cause hydroplaning on runways but doesn't pose the same immediate risk as freezing rain when it comes to aircraft performance. Hail poses a serious threat primarily due to the potential for structural damage to aircraft during flight; however, it does not create the same persistent and hazardous conditions as freezing rain does. Therefore, freezing rain stands out as the most hazardous type of precipitation for aviation operations.