Vitamin D3 should be stored at room temperature, in a cool dry place. Preferably in a medicine cabinet or pantry. However, it is perfectly fine to store them in the freezer or refrigerator.
If Vitamin D3 is traveling through extreme temperatures, the quality/potency will not be degraded in any way. However, if the package sits outside for days in extreme heat and the softgels melt together, this would obviously cause problems with consuming the individual softgels. For this reason, among others, we highly recommend following along with your tracking information provided with each order, to know exactly when your products will arrive.