What to wear under cap and gown at graduation ceremony?

Hey, my high school graduation is tomorrow and I need help deciding what to wear under my cap and gown (I'm a guy by the way). I am required to wear a dress shirt and tie under the blue robe they gave us (which covers my whole body), and wearing a suit is optional. Do you think that it would be okay to wear a robe, a suit, and a dress shirt in 80 degree whether? I think I would look more classy in the suit, but I'm just afraid it will be too hot. Any ideas?