[schleyfox]

Seriously. Good pairs of slacks are about as comfortable as you can get in any situation. Part of the genius is the variety in materials that go in. You have everything from lightweight, super breathable pants perfect for the summer (when jeans and even khakis become miserable in any humidity) to thicker wool trousers that will feel comfortable even in the middle of a blizzard.

That said, the peak of summer comfort is seersucker, but I won't even don that often because it does make you look like an anachronistic dandy.