They need to be protected from freezing. See dispersible granules. Dispersible granules are also called dry flowable formulations. They are small-sized granules that pour from a container like a liquid, but do not stick to the sides of the container and do not need to be protected from freezing. They are virtually dust-free and disperse readily in water to form a suspension.
Fumigants are liquids which turn into a gas after application.
They generally are used for soil fumigation. Most older fungicides sprayed on leaves and fruit are of this type. Most protectant fungicides are relatively stable by themselves. Generally they are relatively insoluble in water and resist removal or chemical change by water, yet must be toxic to fungi. Often a chemical change is brought about by the fungus, the host, or the environment before toxicity occurs.