SkyWest ERJ 175 Limitations Practice Test

Icing conditions hinge on two factors: the air being cold enough and the presence of visible moisture. When the outside air temperature on the ground or the Total Air Temperature in flight is 10°C or below, icing can begin only if there is visible moisture in the air. The key is moisture; without it, cold air alone won’t create ice on the aircraft surfaces.

Visible moisture means any form you can see in the air, such as clouds, fog with visibility, rain, drizzle, sleet, snow, or even ice crystals. While ice crystals can be part of high-altitude clouds, the standard condition for potential icing specifically emphasizes visible moisture in any form—that’s what allows supercooled droplets to strike and freeze on contact with the aircraft.

So, the best answer is that icing conditions may exist when the temperature is 10°C or below and visible moisture in any form is present. Dry air would not produce icing, and restricting moisture to just snow or just ice crystals misses the broader condition that icing depends on visible moisture in any form.