👉 Sleetiness is a weather phenomenon that occurs when tiny ice crystals form on snow or frost, which can be in the form of small, sharp pieces. These ice crystals fall from the sky and land as precipitation, usually falling in the form of snow or rain. Sleetiness can occur in many parts of the world, but it's most common in the United States during winter months. Sleetiness is a natural occurrence that occurs when tiny ice crystals fall from the sky onto the ground.