If you ever want to know what the warmest spots in your house are during the winter, just follow a cat. Please see exhibit A.
This is Payton sitting in the window sill. This is Payton sitting in the window sill directly above the heating vent. He realized that when the curtains are closed, the hot air is forced directly upwards and it creates a pocket of warmth in an otherwise incredibly drafty house. Clever, my bionic cat, very clever.