I seem to see her setting off from a posting station in a snow-storm with thirty degrees of frost.
我仿佛看到她在三十度的霜冻暴风雪中从驿站出发。
英语百科
Degree of frost
(重定向自Degrees of frost)
A degree of frost is a non-standard unit of measure for air temperature meaning degrees below melting point (also known as "freezing point") of water (0 degrees Celsius or 32 degrees Fahrenheit). "Degree" in this case can refer to degree Celsius or Fahrenheit.