Here, thermal ratings, ranging from static to quasi-dynamic to dynamic, will be compared in an effort to show the extent to which real-time weather conditions can improve a thermal rating. All thermal-rating methods will be applied to a span of a high voltage transmission line located in British Columbia. Air temperature, wind speed, and wind direction observations from nearby weather stations will be averaged over different time periods for quasi-dynamic thermal ratings, and the real-time values will be used in the dynamic thermal rating. Quasi-dynamic thermal ratings will be developed that incorporate averaged and real-time values of weather conditions. Dynamic thermal ratings will be computed using ensemble numerical weather model output of the same parameters at every point along the transmission line span. Finally, probabilistic dynamic thermal rating forecasts will be produced using ensemble output to supply a quality thermal overload risk assessment product.