Which weather observation would most likely indicate freezing rain conditions?

Freezing rain conditions typically occur when there is a layer of cold air aloft, which is situated above a warmer surface. This situation creates an environment where precipitation, such as rain, falls through the colder air and begins to freeze upon contact with surface objects that are at or below freezing temperatures.

In this scenario, the warm ground supports raindrops that do not freeze until they meet colder surfaces, leading to ice accumulation that can create hazardous conditions. This phenomenon often arises when warm air flows over a colder surface, resulting in the characteristic freezing rain, while other options do not align with the specific atmospheric dynamics required for freezing rain.

Heavy snow accumulation is indicative of a different kind of winter weather that involves sustained low temperatures and typically occurs in conditions where precipitation falls as snow rather than rain. Mild temperatures with high humidity suggest warmer weather patterns, which would not produce freezing rain. Clear skies with low winds indicate stable, calm weather conditions unlikely to lead to precipitation at all. Thus, cold air existing above warmer ground is the critical factor for the formation of freezing rain.