Freezing rain refers to the rain that falls through a shallow layer of cold temperature at zero degree Celsius or below zero degree Celsius near the earth surface. Celsius and Fahrenheit are two types of measurement that are used to measure temperature. The freezing temperature of water is zero degree Celsius. Zero degree Celsius is the same thing as 32 degree Fahrenheit.
Thus, the thermometer reading that is expected from a thermometer near the earth's surface during a period of freezing rain is 32 degree Fahrenheit.