The chromatic dispersion of optical fiber is a limiting factor in the increase of optical communications transmission bitrates. Chirped Fiber Bragg Gratings submitted to temperature gradients can provide tuneable dispersion compensation, being the tuneability achieved by an appropriate control of the applied temperature gradient. In this work we propose a numerical model that describes heat transfer mechanisms along the fiber grating and its surroundings to obtain a temperature distribution along the fiber grating longitudinal axis. This model, which enables the subsequent modeling of the grating dispersion, demonstrated that the temperature distribution in a steady state is linear. The subsequent modeling of the fiber grating chromatic dispersion agreed with experimental results.