||Harm due to global warming and the heat island effect to the urban environment has attracted scholarly attention. To explore differences in the thermal environment in the city and the reasons for these, we chose 55 fixed sample points from 7 land-use categories in Xi'an City and conducted a 3-year field measurement on the meteorological data of summer. In this research, 21 sample sites with different urban spatial features were screened and the temporal and spatial variability of the heat island intensity and physiological equivalent temperature in the summer daytime analyzed. Then 15 urban spatial indicator values of the research sample sites were calculated and bivariate correlations and regression analyses employing meteorological parameters conducted to probe their relationship. Results confirm building footprint ratio as the strongest predictive factor, explaining around 66% of the air temperature variability in the city. The green cover ratio is also a strong predictive factor, explaining approximately 50% of the variability of the heat island intensity. Finally, the reasonable range of urban planning indicator values were determined according to the threshold of designer indicators in China's Design Standard for the Thermal Environment of Urban Residential Areas. Accordingly, building footprint ratio should not be greater than 23.8%, the green cover ratio should not be less than 30%, and the green space ratio should not be lower than 19.5%. This study provides recommendations for developing environmental urban planning strategies.