Where can visible moisture be found that contributes to icing risk?

• A. In clouds, fog, rain, or drizzle
• B. In clear air only
• C. Only in freezing rain
• D. Only near thunderstorms

Answer: (A)

Visible moisture is the liquid water droplets you can see in the air—found in clouds, fog, rain, or drizzle. When these droplets are liquid and the air is at or below freezing, they can strike an aircraft and freeze on contact, building up ice. That’s why moisture in clouds, fog, rain, or drizzle is what creates icing risk. Clear air has no visible droplets, so it doesn’t pose icing risk. Freezing rain is just one form of visible moisture, but icing isn’t limited to that scenario, and icing can occur with other cloud types and fog as well, not only near thunderstorms.