It depends on what season it is when determining the best time to go fishing. During the spring and fall, it is best to go in the afternoon and early evening. During the summer, it is best to go early morning and early sundown.
Fish stay in the warmer parts of the water, but avoid hot water. During the spring and fall, the top layer of the water is warmest when the sun is directly overhead. During the summer, fish avoid the hot top layer during the middle of the day, but in the early morning and early evening time when it's a little cooler, fishers are more likely to easily catch fish.