The actual CMB temperature is thought to be ~3000 K with a redshift of z = 1089, but that result comes from a specific model that is the CDM (cold dark matter) big bang cosmology. In the big bang, the CMB would be expanding at 99.91%c, but different cosmologies result in a range of predictions and the shrinking universe has a really cold interpretation for the CMB, just 0.64 K at z = 1089. In today's epoch, this temperature would be equivalent to the ionization energy of hydrogen at 13.6 eV, which is 158,000 K...a little bit warmer than the CMB.
In addition, very slight CMB temperature difference is called the CMB dipole, points the direction that the earth is moving through the cosmos. This arrow of time shows our path through the cosmos and defines both an origin and a destiny.