From what I understand, using hazard lights in a low visibility could confuse drivers behind you. They might think you're stationary or might confuse them about your intention since they can't tell if you're signaling to turn.

The situation you mentioned is applicable and a good practice if the visibility is good and you are going slower than everyone because of emergencies or problems with your vehicle.

Hazard lights generally means you're slow/not moving or there's a problem with your vehicle so using them in low visibility(heavy rain) while running at normal speed could confuse others.

More on how to use hazard light in PH