Is there some type of Thermal Ceiling?

[Plasma]

Temperature can't get lower than absolute zero, so is there some point in which it can't get higher?

 

[cesiumfrog]

In some situations there is, for example you cannot focus sunlight to heat something above the temperature of the sun.

 

[DaveC426913]

I suppose one upper limit of temperature would be when molecules have enough kinetic energy to be moving at near c. Of course, there's still the issue of how dense the distribution of those atoms are. And then you could always add IR EM.

 

[Hurkyl]

Temperature cannot be hotter than negative zero.

 

[Crosson]

I suppose one upper limit of temperature would be when molecules have enough kinetic energy to be moving at near c.

Kinetic energy can be large without bound, all it does is add more nines i.e. .99999c instead of .999c.

As an upper limit, too much concentrated energy will rip a (black) hole in the universe. It would be quite a spectacle to watch a motor with 10^60 horsepower rip itself into a black hole.