A pilot must make sure that the airframe is clear of icing before departure, and this is a common problem during winter operations. Airframe icing on the ground is similar to in-flight icing, in that the water droplets need some reason to freeze onto the airframe. For starters, water needs to be present (visible moisture is another term for this), and there needs to be a component that is below 0ºC, whether that be the air, the airframe itself (often the case on a winter's morning), or the water droplets (SCWDs - Super-cooled water droplets, water that exists in a liquid form below 0ºC). The worst icing occurs when the airframe is cold and water or rain droplets freeze directly onto it, creating hard lumps on the wing that destroy the wing's airflow on take-off.

There are other types of icing that can happen to an aircraft on the ground. In fact, hoar frost can be quite common, particularly if an airframe is very cold and the air contains a high relative humidity, allowing the water vapour to turn straight into ice crystals on the airframe by deposition (the opposite of sublimation). Even considering this, there is still only one good answer here.