Strong lattice anharmonicity fundamentally alters phonon dynamics and challenges the conventional phonon quasiparticle description of thermal transport. Using ${\mathrm{Sn}}_2{\mathrm{S}}_3$ as a representative strongly anharmonic crystal, we investigate the role of temperature-induced phonon renormalization on lattice thermal conductivity by combining the temperature-dependent effective potential method with the Wigner transport equation, which explicitly captures both particlelike and coherent phonon transport channels. We show that theoretical descriptions based on unrenormalized zero-temperature interatomic force constants systematically underestimate the lattice thermal conductivity, while one-shot finite-temperature fitting approaches significantly overestimate it. By explicitly accounting for temperature-dependent renormalization of both harmonic and anharmonic interactions, we achieve quantitative agreement with experimental measurements over a wide temperature range. Our analysis reveals that although phonon dispersions exhibit only moderate temperature-induced changes, phonon lifetimes are substantially enhanced due to a pronounced reduction in effective cubic anharmonicity. This enhancement activates significant heat-carrying contributions from low- and intermediate-frequency optical phonons, strengthening the particlelike transport channel. In contrast, the coherent contribution to thermal transport is suppressed with thermal renormalization. These results establish temperature-induced anharmonic renormalization as a key mechanism governing thermal transport in ${\mathrm{Sn}}_2{\mathrm{S}}_3$ and provide an alternative perspective for understanding heat conduction in strongly anharmonic crystalline solids.

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• Anharmonic lattice dynamics
• Heat transfer
• Lattice thermal conductivity
• Ab initio molecular dynamics
• Boltzmann theory
• Density functional calculations