For those entities that use magnesium chloride as their deicing agent of choice, the timing of mag-chloride application is critical. For instance, magnesium chloride must not be applied before the early stages of a storm. The key is – the road surface has to be wet for the magnesium chloride to work effectively. Instead of applying the product pre-emptively, spend the time before the expected storm mobilizing so that the magnesium chloride can be applied as soon as the storm strikes and the roads are wet.