Instrument Flight Rules (IFR) Practice Exam 2025 – The All-in-One Guide to Master Your IFR Certification!

Rime ice is most likely to form in stratiform clouds. This type of ice develops when supercooled water droplets present in clouds freeze upon contact with a surface that is at or below freezing. Stratiform clouds, which are typically widespread and layer-like, often contain these supercooled droplets that can lead to the formation of rime ice.

This condition is particularly relevant for pilots because flying through thick stratiform clouds increases the likelihood of encountering this hazardous ice. When small, supercooled water droplets strike an aircraft, they can freeze on impact, creating a rough, white ice known as rime ice. It often accumulates on leading edges and other surfaces where airflow is disrupted.

In contrast, clear air turbulence does not typically contain moisture conducive to forming rime ice, and high humidity conditions alone do not guarantee ice formation without the presence of supercooled water droplets. Ground operations can also expose aircraft to freezing conditions, but without the ice-forming mechanisms provided by cloud presence, rime ice is less likely to develop. The stratiform cloud environment directly increases the risk and prevalence of rime ice formation.