• Temperature has a more significant effect than cycle count on the degradation of P-wave velocity and tensile strength of granite.
• Damage evolution exhibits a dual-threshold behavior: degradation accelerates markedly above 400 °C and stabilizes after 5 thermal cycles.
• Fracture surfaces transition from planar to rugged with increasing temperature, with peak-valley height differences at 600 °C being about three times those at 200 °C.
• A novel failure precursor indicator based on acoustic emission energy entropy provides reliable early-warning signals for impending rock failure.