I have seen people using hazard lights in heavy rains. Even there, it is referred to as parking lights!
It can be dangerous. Imagine this situation. It raining like cars & dogs. Visibility is down to minimum. And all drivers are using their hazard lights even though their cars are not parked. You are on a 4 lane highway, on the fast lane. Now, there is actually a broken down car in the fast lane with it's hazard lights ON. you think that even it is moving, like all the other cars, as visibility is minimum.
By the time you realize, it is too late. Whose fault is it?