It's become somewhat of a stereotype that, when we hear "Ancient Greece", we imagine endless idyll, peace, tranquility, warmth, culture, theater and togas with sandals.
How did they prepare for the Winter though?
Just for clarification, the Greeks did not wear togas, rather himations, chitons, and peplos. Togas were an Etruscan-influenced Roman style, and differed from the green garb both in fastening, drape, and style.
The met has a nice overview of Greek attire here, which includes an overview of how the components were layered for comfort as well.