How hot was the Big Bang?
The big bang is the instant when the primordial singularity became the universe. A singularity is defined as an infinitely dense, infinitely hot and infinitesimally small point. All our math breaks down as we approach the singularity, and so the answer is 'infinite temperature'.
However, based on observations of distant objects and measurements of the cosmic background radiation, scientists have deduced the temperature at the instant of the Big Bang as