Do you know why the line is, “I can see clearly now the rain is gone”? Because we cannot see as well in the rain as we can outside of rain.
When it’s raining, your lights should be on (not your HIGH beams, not your hazards!) so you can be easily seen in the dreary weather.
Also, and this applies ALL THE TIME, if you cannot see the reflective part of the mirror of another vehicle, then they cannot see you, so stay out of other vehicles blind spots!