A method has been developed to measure thermal properties of a media from time‐dependent temperature distributions. Data from a number of locations and times are used to construct polynomial approximations to the observed phenomenon. Derivatives appearing in the differential equation describing the temperature field are evaluated from the polynomials and are then used to determine the parameters in the equations. Two examples are included. The first is a measurement of the thermal diffusivity of copper. A simple experiment is shown to give results over a range of 100°C which agree with the literature to within 3%. The second is an investigation of the space dependence of the heat generation due to nuclear radiation in a metal cylinder placed in a reactor.