Rime ice forms when supercooled water droplets freeze onto surfaces. In the atmosphere, there are three basic types of rime ice:

• Soft rime forms when supercooled water freezes under calm wind conditions. It is milky and crystalline, like sugar, and similar to hoar frost.
• Hard rime forms by rapid freezing of supercooled water under at least moderate wind conditions. The droplets freeze more or less individually, leaving air gaps.
• Clear ice forms by slow freezing of supercooled water. Clear ice is typically transparent and homogeneous. Its amorphous and dense structure makes it adhesive.