This study analysed the spatial temperature differences among urban structural environments with different meteorological elements, and radiant fluxes in the energy balance system using surface characteristics. A simulation was performed by evaluating the radiant flux, using the SOlar and LongWave Environmental Irradiance Geometry (SOLWEIG) model. The simulation reading of upward longwave radiant flux, which shows the surface effect in an urban landscape, showed a slightly higher daily maximum than actual value for man-made structures but it was very accurate for natural areas. Most of the R2 values were 0.8–0.9 or higher, and the RMSE was 19–60 w/m2. The net radiant fluxes of the ten study sites were similar. According to the local climate zone (LCZ) classification, even in areas with artificial structures, the highest and mean radiant temperatures were observed in LCZ 2 and 3. In Seoul metropolitan area, the residential areas of LCZ 2 and 3, which were built 30 to 40 years ago, have very high heat stress. They have recently been changed to LCZ 4 and 6 through urban redevelopment and regeneration. Through such urban surface management, it is expected that high heat stress in Seoul will be relieved by 1–3 °C.