Fish behavior is largely affected by the amount of sunlight, which depends on cloudiness and precipitation.
Rain brings a large amount of nutrients, which is why cloudy days with intermittent rains drastically change fish behavior and increase the chance of a good catch.
Low lighting makes it harder for predators to hunt. Good lighting conditions, on the contrary, make it harder for non-predatory fish to evade attacks, causing them to move to higher depths or hide in the shade of trees and bushes.