This paper is a part of the work in developing a software that predicts IR signatures from objects in the scene by considering the direct and diffuse solar irradiations, the atmospheric convection and the conduction within objects. The thermal information of the objects and their background is essential for understanding the IR signature characteristics from the scene. The thermal contrast between the objects and the background is then used to obtain their infrared radiation contrast which is the important signal in identifying the objects. We considered the composite heat transfer modes including conduction, convection and spectral solar irradiation on the objects within a scene to calculate the surface temperature distribution. The radiative energy components included in the thermal analyses are consisted of the direct and diffuse solar irradiances and sky thermal irradiation, while the thermal conduction within the object is approximated as one-dimensional heat transfer into the depth. The measured diurnal surface temperature variations on the three different test plates facing east, south and west respectively are fairly well compared with the modeled results obtained from the software developed in this study and a commercial software. A complete set of measured data including the plate temperature together with the detailed weather information and the irradiation data can be valuable reference for future study.