Exactly what I was thinking. When a colder substance (lower energy) comes into contact with a warmer substance (higher energy), the temperature (energy) levels equalize, which makes the warmer body colder and the colder body warmer. That's why we put ice cubes in our drinks and also a heating coil (the kind people use to heat water, commonly used when travelling) to make our morning tea.

If Wim's warmer body meets a colder substance, the two temperatures (energy levels) will equalize. You can't get around this basic law of physics, although insulating materials like a dry suit or a wet suit would help stave things off. Ergo, Wim has to be generating a lot of heat internally.

Heat is never "free." Some process has to occur to generate heat and something is always consumed in said process (e.g. nuclear fusion in a star, burning wood, or human metabolism).

I wonder how much Wim eats? It's hard for me to imagine a human body acting in such a way as to generate sufficient heat to dry wet sheets and melt surrounding snow, but that's the only explanation I can think of.

Has anyone seen anything on the net that explains this phenomenom?