September is the perfect month for a sail boat ride. You can still bring a sweater, but also a cooler for your favorite beverage.
You can still wear sandals, but with a choice of shorts or pants. you can still wear a hat, but you can choose if it is cotton or wool.
The foliage hasn't quite come out yet, so you can see the shore in the same state it has been all summer but without all the tourists, and heat.
I dont have a sailboat, nor does anyone I know, but if you have access to a friend or family member who does...
I suggest on this long weekend, GO SAING!