Which hidden factor can make a desk beside a cold window feel chilly even when the thermostat across the room still reads 22 C?

Answer: Cold surfaces pull radiant heat

Humidity suddenly spikes — Humidity can change how sweat evaporates, but it does not explain the special chill of sitting beside a cold pane. You can feel colder near the window even if room humidity and air temperature barely change. The missing channel is radiation: your warm body exchanges infrared energy with surrounding surfaces. Cold glass increases that radiant heat loss from the side facing it.

Cold surfaces pull radiant heat ✓ — Correct. Humans do not exchange heat only with air; we also radiate heat to walls, windows, floors, and ceilings. A cold window lowers the local mean radiant temperature, so your body can lose heat toward it even while the air thermometer says 22 C. This is why radiant floors or warmer interior surfaces can feel comfortable at lower air temperatures than forced cold air would suggest.

Air temperature tells all — Air temperature is the visible number, but it does not tell the whole comfort story. A normal wall thermostat mainly measures air near its sensor, not the surface temperatures surrounding your body. Air movement can matter, but the cold-window effect can appear even without a strong breeze. The larger surprise is that room surfaces are part of the temperature you feel.