Whereas absolute zero corresponds to complete absence of molecular motion, there is no obvious analogy with a maximum temperature. Ultimately, this is largely due to the fact that there are still unresolved questions about the properties of matter at very small length scales. The current model that describes the properties and interactions of elementary particles, called the Standard Model, indicates that the maximum theoretical temperature is approximately 1032 Kelvin. This temperature is called the Planck temperature, named after the physicist Max Planck. Its hard to even come up with an analogy for just how hot this temperature is. For example, the interior of the Sun is only 107 K. It is believed that at one point, the temperature of the Universe was at the Planck temperature. However, this likely occurred an extremely brief time (10-43 seconds) after the Big Bang when the Universe had a diameter of only 10-35 meters.

No one has been able to figure out what would even happen if it was possible to exceed the Planck temperature. At that point, there are no theories that describe how matter would behave.