Techniques are described for generating earth sub-surface thermal characteristics over an area include collecting real-time weather data and earth data for a plurality of locations associated with an underground electrical cable and calculating earth thermal properties at the plurality of locations based on the real-time weather data and the measured earth data by an iterative process. The calculated earth thermal properties at two or more of the plurality of locations are interpolated to determine interpolated earth thermal properties at another location associated with the underground electrical cable and a wide-area thermal property map created from at least some of the calculated earth thermal properties and the interpolated earth thermal properties.