Quite the Range
Earth may seem like a place with a lot of diversity, and in many ways, it is. Our planet is home to organisms that are smaller than the tip of a needle, while a few are the size of a building (like the blue whale) or a person (like the Nomura’s jellyfish).
But in truth, many things on Earth are really rather tame. At least, they are tame as far as our experiences go. The temperature of our environment is one example. It may vary by 50 degrees from winter to summer, give or take a little, but that really isn't much of a difference in the grand scheme of things.
For comparison, the hottest temperature, known as Planck temperature, hits more than 100 million million million million million degrees, or 1032 K. As has been noted by NOVA Online editor-in-chief Peter Tyson, "You just can’t put this kind of temperature into perspective. There’s simply no way to wrap your head around this number. Saying that 1032 K is hot is like saying that the universe occupies some space."
The Theory of Everything
If we try to go any higher than Planck temperature, physics breaks. Literally. Gravity grows as strong as the other fundamental forces, and, in essence, they all become one force.
That is what we are looking for: the math behind that one force. That is the theory of everything, a kind of quantum gravity. Unfortunately, for now, it is beyond us, and so the highest temperature remains the ceiling, as it were. But now I am getting a bit off topic.
The point, however, is that the hottest hot and the coldest cold will blow your mind, and you should check out the below infographic from BBC Future to get a better idea of what hot and cold really mean.