Why do you restrict yourself to summer fishing? Crappie bite the year around.
If it is a light rain I will sometimes fish from my slip. However if it is a heavy rainstorm I don't fish.
I don't use my boat on the lake when it is raining unless it comes up unexpected. I don't like lightning nor do I care much for being wet. If I am on the lake when it started raining I will head for the nearest bridge or my slip, which ever is the closest.
I don't mind fishing when it's snowing but that doesn't happen much here.