A major snowstorm is expected here in the northeast tomorrow. In preparation, salt trucks have been out in force across the region.
Rock Salt – large pieces of NaCl – removes snow and ice from roads and walkways by lowering the freezing point of water. Essentially, it melts frozen precipitation into a briny liquid and makes it harder to re-freeze, even if the air temperature is below freezing. In extremely cold conditions, however, when temperatures fall below 15°F, rock salt becomes less effective at de-icing surfaces.
While salting roads can help reduce traffic accidents, it does have negative environmental impacts. So, as with diet, it is best to use salt sparingly.