Quantum metrology exploits quantum-mechanical principles and certain non-classical resources to achieve high-precision parameter estimation that surpasses the classical shot-noise limit. Quantum criticality is one of the most common resources and is widely used in various protocols of quantum metrology. However, in practical settings, the quantum probe inevitably interacts with its environment, and the environmental thermal noise typically degrades or even completely destroys the quantum advantage established by criticality. As a consequence, most existing criticality-enhanced schemes are limited to zero or ultra-low temperatures, which severely restricts their experimental feasibility. To address this issue, we propose a unified critical metrology scheme based on a pure-dephasing-type probe-reservoir interaction, which is immune to the decoherence induced by thermal noise. In our scheme, we employ a spin-chain probe to sense the temperature of a dissipative bosonic reservoir. Going beyond the conventional approaches that rely on the weak-coupling approximation, we account for the strong probe–reservoir coupling effect via a polaron transformation, which fully decouples the probe and the reservoir. Our analysis reveals that the strong coupling induces a thermal phase transition within the standard framework of Landau mean-field theory. At the critical temperature, we find that both the quantum Fisher information and the signal-to-noise ratio exhibit a power-law divergence. Our criticality-enhanced scheme eliminates the stringent requirement for cooling and can be generalized to the case of dissipation-type interaction. These findings significantly broaden the scope of critical metrology and offer a practical route toward high-precision quantum metrology under realistic conditions.