  We show that the performance of critical quantum metrology protocols,
counter-intuitively, can be enhanced by finite temperature. We consider a
toy-model squeezing Hamiltonian, the Lipkin-Meshkov-Glick model and the
paradigmatic Ising model. We show that the temperature enhancement of the
quantum Fisher information can be achieved by adiabatic preparation of the
critical state and by preparing it directly in the proximity of the critical
point. We also find a relatively simple, however, non-optimal measurement
capable of harnessing finite temperature to increase the parameter estimation
sensitivity. Therefore, we argue that temperature can be considered as a
resource in critical quantum metrology.
