-- Last Updated: Dec-28-12 6:17 PM EST --
My black vinyl gunwales get terribly hot under a strong summer sun, but I've never noticed any such thing with my aluminum gunwales, which have a light gray-brown color.
Hot aluminum will feel hotter, and cold aluminum will feel colder, than will be the case with many other materials at the same temperature due to the fact it's an excellent heat conductor. In the case of my aluminum gunwales, it seems that they do not get all that much hotter than the air, so they don't feel terribly hot either.
Actually, even when my black vinyl gunwales get "terribly hot", it's not unbearable. It's something that'll make you wince if accidentally resting your forearm flush on that black surface, but it's not something that would affect my overall happiness with a boat all that much. When they are hot like that I also think it's a lot worse for the sudden "friction heat" when rubbing a hand along the gunwale than at other times, but I think simply grabbing the gunwale is still okay to do. It's certainly okay if your hands are a little bit wet.