When Cool Turns Cold

My unofficial claim that Low temperature prevents the body from functioning properly still stands (unofficially stood).
You do not need to get hypothermia to have malfunctioned brain and frozen limbs.
While hypothermia might lead to death, the accidental case of brain freezing is far from what defines hypothermia.
As opposed to natural coldness caused by seasonal changes (i.e Winter), accidental brain freezing is mainly caused by prolonged confinement in artificially cold air. (read : air-conditioning).

Cakes. Overly high temperature, you'll risk getting a burnt end product, inedible. Set it way too low, it might not rise nicely. Either way, you flunk baking.

Enzymes and other living organisms?
Just like many other living things on Earth, we; without exception, function the best at optimal temperature.

I'm freezing, uncomfortably cold...
While the hot sun leaves its scorching power on everything that catches its rays, it feels weird to be in this artificially cold office space. Not cool, its Cold.