The inside of a castle would have been roughly the same temperature as a pile of rocks in the same climate. In hot dry climates it would have been cooler than the heat of day, especially if they whitewashed the roof. In cold climates it was perpetually below what we would call comfortable.

Medieval castles were notoriously freezing during the winter, often reaching indoor temperatures barely above the freezing point of water. The massive stone walls acted as "heat sinks," absorbing any warmth and radiating cold back into the rooms. To combat this, residents utilized massive central fireplaces and portable braziers filled with glowing coals. Privacy was often sacrificed for warmth, as entire households would sleep in the same room or use heavy wooden beds with "four-poster" curtains to trap body heat. Windows were small and usually lacked glass, instead being covered by shutters or heavy oiled parchment. Floors were covered in rushes or straw to provide a layer of insulation, and the walls were draped in thick tapestries to block drafts. Clothing was the primary defense; even the nobility wore multiple layers of wool and fur-lined robes while indoors. Despite these efforts, life in a castle during a harsh European winter was a constant struggle against dampness, drafts, and bone-chilling cold.