  Attention is paid to the fact that temperature of a classical black hole can
be derived from the extremality condition of its free energy with respect to
variation of the mass of a hole. For a quantum Schwarzschild black hole
evaporating massless particles the same condition is shown to result in the
following one-loop temperature $T=(8\pi M)^{-1} (1+\sigma (8\pi M^2)^{-1})$ and
entropy $S = 4\pi M^2 - \sigma\log M$ expressed in terms of the effective mass
$M$ of a hole together with its radiation and the integral of the conformal
anomaly $\sigma$ that depends on the field species. Thus, in the given case
quantum corrections to $T$ and $S$ turn out to be completely provided by the
anomaly. When it is absent ($\sigma=0$), which happens in a number of
supersymmetric models, the one-loop expressions of $T$ and $S$ preserve the
classical form. On the other hand, if the anomaly is negative ($\sigma<0$) an
evaporating quantum hole seems to cease to heat up when its mass reaches the
Planck scales.
