Which types of clouds are most likely to produce severe icing conditions?

Cumulus and cumulonimbus clouds are associated with severe weather phenomena, including severe icing conditions. These types of clouds are formed through strong updrafts and significant atmospheric instability, which leads to the development of vertical growth and large moisture content.

Cumulonimbus clouds, in particular, are towering clouds often linked to thunderstorms. Within these clouds, supercooled water droplets can exist at temperatures below freezing, especially in the upper parts of the cloud where the temperatures are lower. As aircraft ascend or descend through these clouds, they can encounter this supercooled liquid water, leading to the formation of ice on the aircraft's surfaces, which can be particularly hazardous during flight.

While other cloud types can produce icing, they typically do not contain the vertical development and intense moisture characteristics seen in cumulus and cumulonimbus clouds, making them less likely to produce severe icing conditions.