Ice always melts at 32 F, but water does not always freeze at 32 F. It must freeze onto something. However, at -40 F, water freezes spontaneously. If you poured a cup of water out of a window with the air temperature outside at -40 F, the water would freeze before it struck the ground. Wind chill is the combination of wind and temperature and is based on the rate of heat loss from exposed skin such as that of a person or animal. As the wind increases, heat is carried away from the body at an accelerated rate, driving the body temperature down.
Wind chill has no effect on cars or other objects.
On February 11, the temperature dipped to -15 F in the District. That year DC saw a record 54 inches of snow. Hail is a chunk or stone of ice dropped from a thunderstorm. Sleet is frozen rain. Freezing rain is liquid rain that freezes to a surface such as the road or a tree.