Fishing in the light rain is awesome but the heavy rain can stirr up too much bacteria and change the PH of the water for a few days. There's a pro and con to fishing in the rain. But i have seen bass catching frenzy's prefrontal, during the light rain and when the rain lets up for a while between rain storms.
I think overall its the low light situation that causes the bass to feed more. The weather front also triggers something in there bodies too so they put the feed bag on.
I have hit this frenzy a few times now and i have caught weird colored fish during this time too. They look like white/pink sunfish/crappies. Others that i have met fishing have caught these white/pink fish too. I have no clue as to what they are.
I'm thinking its the frontal plus the moon phases that can cause this feeding frenzy I hit sometimes but not as often as i would like to see. I just can't nail it down as to when it happens. Its probably more complicated than i'm thinking it is. One time fishing from one spot from shore i caught 19 bass back to back. Another time i probably caught about 50lbs of bass, i lost count as to how many bass i caught. Another time me and my son caught doubles for an hour on mepps inline spinners. The inline spinners like mepps and joesfly's seem to be the best lures during this time with cranks second a close second. I swear the fishing is so hot a bare hook would work too. It can be non stop fishing, a bass per cast.
My older brother always told me to stay going and the fish will turn on sooner or later, he was right.