If you are going to repaint in the fall, be sure to use an ablative bottom paint can be out for months and can be pressure washed/ lightly scuffed and put back in the water in the spring ready to go. Hard bottom paint is just that, "hard" when the outerlayer is oxidized - its done, over, no good! The paint will no longer prevent growth after being out for several months and it will NOT work in the spring.
Here is the reason: The copper in the paint oxidizes when exposed to air. Oxidized copper is ineffective for preventing marine growth.
Ablative bottom paint wears away much like a bar of soap. This constantly exposes new, fresh, unoxidized copper. So once you leave your boat out for an extended period, and pressure wash, lightly scuff, or run the boat...you will expose fresh copper that will protect against growth.
So you can paint in the fall as long as you choose a multi-season ablative bottom paint.