An accurate assessment of thermal comfort allows in-time adjustments in design that leads to achieve a more pleasant indoor or outdoor environment. Among the factors that influence human thermal comfort, Mean Radiant Temperature (MRT) is the focus of the present paper. This work proposes a methodology to facilitate the process of recording, measuring and post-processing of MRT. Current techniques used to estimate MRT in urban environments have several challenges among which accuracy and settling time are the major issues. Moreover, the only output is a single value for MRT without the possibility of sensitivity analysis on effective parameters. The method proposed in this paper, called Radiant Ambience Imaging, is established based on two main techniques: thermography and Numerous Vector (NV) numerical method. The MRT is assessed by capturing infrared and HDR images from a polished hemisphere followed by the numerical analysis. The results not only include the value for the MRT at the point of interest but also the share of each radiant object. The process relies merely on electromagnetic radiation fluxes and there is no need for wind effect corrections. It also provides data post-processing to help architects optimize their designs in order to control MRT in practical applications.