What is the primary factor that distinguishes cumulonimbus clouds?

Cumulonimbus clouds are primarily distinguished by their height. These clouds are characterized by their towering vertical development, often reaching significant altitudes where they can extend from low altitudes to heights of 12,000 meters (40,000 feet) or more. They typically develop as a result of intense convective activity, which occurs when warm, moist air rises rapidly. As this air rises, it cools, condenses, and forms the characteristic anvil shape at high altitudes.

While density, color, and shape are important characteristics of clouds in general, the defining feature of cumulonimbus clouds is their great height and the associated weather phenomena they produce, such as thunderstorms, heavy rain, and even severe weather events like tornadoes. This vertical development is what sets cumulonimbus apart from other cloud types, making height the primary distinguishing factor.