How warm should a winter coat be for a cold city?
For real winters (regularly below freezing): insulated or heavy wool, thigh length, with a closure that seals. Fashion coats top out around 40F.
Coat warmth is insulation plus coverage plus sealing. Insulation: down is warmest per weight (600+ fill for city winters); heavy wool (24oz+) is the tailored equivalent and handles damp cold better. Coverage: waist-length jackets leave your legs in the wind; thigh length is the minimum for real cold, knee length for the bitter weeks. Sealing: a storm placket over the zip, cuffs that close, and a collar that actually stands - an open coat is a funnel for wind. The honest test for city use: can you stand still at a bus stop for ten minutes at 25F without misery? Walking generates heat; standing is the audit. If your coat fails the bus stop test, the fix is not a heavier coat, it is a thermal base layer - 80% of the warmth gain at 20% of the bulk.