Double check, but I believe it is 0 K.

Band structure is a 0 K concept.

The ionic temperature is 0 K, which means that the atoms do not move (by default, the nuclei are treated classically). The electronic temperature is more complicated, but it is probably best to consider it also as a 0 K result.

The complication for the electronic case is that we usually apply a Gaussian smearing to the states to improve convergence; however, the typical smearing of 0.1 - 0.2 eV only has a very small effect on the states for most materials (anything with a band-gap greater than ~3*smearing_width). If you actually wanted to compute the thermal effects, you should use Fermi-Dirac smearing.