You should put some salt down before freezing rain to help prevent the rain from freezing on the surfaces.
Roads are salted with road salt before the rain starts to freeze on the surface.
Salt is sprayed on icy roads in the winter to lower the freezing temperature or freezing point of the ice.
Salt sprayed on the road prevents ice from forming in colder temperatures on the road and salt that is sprayed on roads when temperatures are at or below 32 F can help to melt the icy patches of ice on the roads.
So if there's precipitation (snow, sleet, or freezing rain) and the ground is 32 degrees or colder, ice will form on streets and other surfaces.
So, why use salt on roads and other surfaces?
It's simple – salt lowers the freezing point of water, which prevents ice from forming.
Just like when you put salt on your sidewalk or driveway or porch etc it melts the ice and prevents other ice from forming.
Road salt, or sodium chloride, works by lowering the freezing point of water, causing ice to melt even when the temperature is below water's normal freezing point of 32 degrees.
When salt is applied, it dissolves into separate sodium and chloride ions that disrupt the bonds between water molecules.