<p>White Marbles are used as cladding material in heritage structures globally. To develop effective restoration techniques for these heritage structures, it is crucial to thoroughly assess damage. Thermal weathering is one of the crucial causes of damage; however, quantifying the damage is restricted due to the limited correlated non-destructive test facilities. There are challenges in the availability of standard optimized protocols for simulated thermal weathering in marbles to obtain the desired porosity in the stone sample. This study simulates thermal weathering in Makrana marbles, commonly used in the Indian UNESCO World Heritage sites, proposes an optimized weathering protocol, and elucidates the thermal weathering effects on their physico–mechanical properties. A correlation was obtained from the continuous monitoring of ultrasonic pulse velocities and open porosity at different weathering cycles. This paper proposes an optimized method for inducing thermal weathering in fresh marble samples, presents the impact of thermal weathering, and develops a correlation between ultrasonic pulse velocity and open porosity.</p>