jase, as per my understanding on hazard lights, it should be used only in below situations:
1. When there is a breakdown on the road (this is best usage of the flasher lights).
2. When there is an unusual or sudden situation (e.g. accident, road blockage etc ) coming up ahead and you want to warn traffic behind you.
However it is common that hazard lights are used in fog, rain, while towing, for picking/dropping passengers on roadside etc. In my opinion, usage of hazard flashers in these fashions downplay the importance / usefulness of the same.
Edit: Further, in my opinion, using flasher lights while driving in rain/ fog is really bad practice because one may not know if there is genuine breakdown on the road.