Under what temperature conditions can icing occur?

Icing can occur at temperatures nearing 32°F with visible moisture present because this is a critical factor where the temperature is close to the freezing point of water. When water droplets are present in the atmosphere, they can remain in a liquid state even when temperatures are at or just above freezing. This phenomenon is known as supercooled liquid water, which can lead to ice formation on surfaces like aircraft with conditions that favor moisture presence. This is particularly important for small unmanned aircraft systems (sUAS) since any accumulation of ice can significantly affect their performance, stability, and aerodynamics.

The other scenarios presented do not accurately capture the conditions under which icing can occur. For instance, icing does not strictly require temperatures to be below 0 degrees Celsius, as supercooled conditions can lead to icing at near-freezing temperatures. It also isn't limited to only freezing temperatures, nor does it occur solely during warm weather where actual freezing isn't likely. Thus, the presence of moisture along with temperatures near the freezing mark is key in understanding icing conditions for sUAS operations.