thaw

1. To melt a substance, ice for example, by warming it to a temperature greater than the melting point of the substance, or to have frozen contents melted.
2. To free something from the binding action of ice by warming it to a temperature above the melting point of ice.
   
3. A warm spell when ice and snow melt, for example, "January thaw."

In the United States, a period of mild weather popularly supposed to recur each year, in later January; most pronounced in the Northeast and, to a lesser extent, the Midwest.