I imagine when the people wanted a good laugh, they went up and stood before the ark door and laughed. “Why, you said it was going to rain a hundred years ago! Grandpa told me he heard you up here saying it was going to rain, and you're still beating around on this old piece of wood up here. Why don't you get next to yourself?”
But it was God getting ready to confirm a promise and to fulfill a prophecy that His prophet had made. Very unusual! God fulfilling His promise to Noah, while others was laughing. God was also getting ready to make history to show to others, even to this day, that He keeps His Word! No matter how unreal it seems, and unreasonable, He still keeps His Word.