Supercooled rain

From Glossary of Meteorology

supercooled rain

Liquid precipitation at temperatures below freezing.

At midlatitudes, supercooled rain often forms first as an ice crystal or snow in the clouds, which then melts as it falls through an elevated layer of air warmer than freezing before reaching the thick bottom layer of cold air that cools the drop below freezing. A supercooled drop freezes instantly on contact with surfaces such as electrical power lines, trees, and roads during an ice storm.
See glaze.