Abstract Traditionally, the rating of an overhead transmission line is determined under a set of specified and standardized conditions. However, weather conditions along the line change during operation. Therefore, the standard rating of the line might be either underestimated, leading to inefficient utilization of the line, or overestimated, leading to unsecure operation. This is the major drawback of the traditional approach: the so-called dynamic thermal rating (DTR), that takes into account the actual operating conditions along the line to determine the rating, is today a critical need. In this paper, we develop a comprehensive methodology for exploring all necessary information about stochastic processes of environmental variables surrounding and along the line using available data. The results can be used as input to determine the actual rating of the considered transmission line to enhance the determination of the rating for transmission lines.