Adapting my usual wardrobe for colder weather involves a few extra layers.

Base: jeans, black t-shirt, possibly a fleece vest, leather shoes.

Cold weather (~20F or below): beanie, leather jacket (lined), scarf, possibly a heavy sweater depending on the duration of being outside, and gloves. Also athletic tights (more insulation than just plain jeans).

Really, it doesn't take much.

It doesn't take much because you stay indoor most of the time. Spend a day outdoor in freezing weather to see the difference :)

No, that's dress for wandering around Chicago in Dec/Jan.

Sunlight daytime and night are somewhat different. And yes, I do tend to run warm (body mass and musculature help).

Indoors: shorts and a T.

Definitely. I live in Ireland and wear the same clothes year round (in the winter I add a scarf and gloves). Definitely not possible growing up in Atlanta.

Blue jeans, black t-shirt, light jumper (I have about 20 in different colors), and soccer flats. I have a suit which I have to wear about once a year.

I actually was in New York for two weeks last winter. I wore double hoodies, thick socks and boots, but still wore t-shirts.

My wardrobe follows many of these mechanics - jeans, t-shirt, hoodie. In the winter (I live in Waterloo, Ontario) I just add layers. Sometimes more shirts, sometimes long underwear, and always a jacket, hat, gloves etc. It's usually pretty warm inside, so the core pieces don't change.