I see that I am mistaken: The temperature is a function of the particles energy, not its speed. The energy at light speed is infinite, so that doesn't really po

I see that I am mistaken: The temperature is a function of the particles energy, not its speed. The energy at light speed is infinite, so that doesn't really pose a temperature limit. There does however seem to be an quite widely assumed maximum temperature: the Planck temperature of about 1.417×10^32 Kelvin.