  Quantum phase transitions occur when quantum fluctuation destroys order at
zero temperature. With an increase in temperature, normally the thermal
fluctuation wipes out any signs of this transition. Here we identify a physical
quantity that shows non-analytic behaviour at finite temperatures, when an
interaction parameter is quenched across the line of quantum phase transition.
This quantity under consideration is the long time limit of a form of quantum
fidelity. Our treatment is analytic for XY chain and 2D Kitaev model and is
numerical for a 3D Hamiltonian applicable to Weyl semimetals.
