Apparatus and associated devices relate to a system for measuring a maximum size of super-cooled water droplets in a cloud atmosphere. The system includes a housing having a convex exterior surface on a forward end and having stabilizers projecting from an aft end. The system includes a gimballed mounting mechanism configured to attach the housing to an aircraft while permitting the housing to freely pitch and yaw with respect to the aircraft. When an airstream engages the stabilizers, the housing aligns with a direction of the engaging airstream. The system includes a sequence of indices on a corresponding sequence of ice-accretion regions of the convex exterior surface, each of the sequence of indices visible in the absence of ice accretion. The forward-most ice-free one of the sequence of indices is indicative of a maximum size of super-cooled water droplets.