You will catch more fish when it’s raining.
In my experience this is not true. I have caught plenty of fish when it was raining but I can’t say that the quantity of fish caught was any greater than when it wasn’t raining. In fact the longer it rains, they harder it is to catch fish. When rivers become flooded from heavy rain the water visibility becomes really bad. Also you are fishing for the same amount of fish in a larger volume of water. This decreases your chances of hooking as many fishies. Smallmouth fishing can really suck after heavy flooding rain. If it’s going to rain while I’m out on the river I would prefer sunshine interrupted by a slight drizzle followed by more sunshine.