It has been well recognized in the earth science community that subsurface ground temperatures and surface air temperatures are related. A present-day subsurface temperature versus depth profile can be used for a reconstruction of a climate history, because the effect of air temperature fluctuations will propagate downward into the earth. In this paper, instrumental records from the Xi'an Meteorological Station from 1951 and subsurface temperature measurements from 16 boreholes are analyzed for an understanding of thermal environmental changes across the ground surface in Xi'an, Shaanxi Province, central China. Linear- regression analysis of meteorological data from 1951 to 2010 shows warming trends of 3.71 ℃/100a in the annual mean, 2.03 ℃/100a in the annual maximum, and 5.14 ℃/100a in the annual minimum air temperatures, all substantially greater than the national and global rates. The warming trend in the annual mean surface air temperature (SAT) was even more stronger, at 9.01 ℃/100a, for the 25-year period from 1986 to 2010 in Xi'an. This warming trend is well preserved in the subsurface temperature records. Six conductive temperature profiles located in both ruraland urban areas were selected for the derivation of the geothermal gradient,the steady state ground surface temperature (GST),and the reduced transient temperatures. Synthetic borehole temperature profiles based on the inferred steady state components and the 25-year SAT warming trend are in general consistent with the observed temperature profiles. A refined analysis of the borehole temperature data further suggests that the onsets and the magnitudes of the GST warming at the six selected borehole sites were respectively 20 years ago at 0.4 ℃, 24 years ago at 0.72 ℃, 26 years ago at 2.18 ℃, 28 years ago at 4.2 ℃, 30 years ago at 2.4 ℃,and 30 years ago at 2.4 ℃. Moreover, there is a pattern in the GST warming, least in the rural areas and greatest in the urbanized areas in Xi'an.