The first step to preserve the historical heritage against global warming effects is understanding how this phenomenon affects the process of material degradation. This impact can be intensified in dense metropolitan areas by the impact of the urban heat island. This research aims to understand whether the cultural heritage located in Mashhad suffers from this phenomenon or not. By comparing the modelled climate data with the observations recorded for Mashhad meteorological station and another station located in a rural area close to the city, the existence of the urban heat island and timing of the phenomenon intensification has been analysed. Our study results show that the rising air temperature combined with the significant city sprawling during 1980-1990 created the urban heat island that the heritage construction suffered.