How about looking at it another way ? When it rains the air temperature usually falls. Prolonged rains generally lead toa drop in water temperature. A sharp drop can reduce the chances of catching tench , in my view, although I don't believe that bream and carp are quite as sensitive.
I've had reasonable catches of tench on showery days - spasmodic showers don't change the water temperature, but light intensity may be reduced, which sometimes means tench will feed for longer into the late morning and early afternoon. By contrast, a hot, still day with bright sunshine means that, on the ponds I fish, tench are reluctant to feed outside the early morning/late evening periods
The above comments relate to stillwater fishing
