A physics-based empirical model is developed to characterize the time varying temperature profile from post-detonation combustion. Fourier-transform infrared signatures are collected from field detonations of RDX-based aluminized high explosives surrounded by an aluminized plastic-bonded spin-cast liner. The rate of change of temperature in the post-detonation combustion fireballs are modeled using a radiative cooling term and a double exponential combustion source term. Optimized nonlinear least-squares fit of the numerical solution of the empirical model to the temperature data yields peak temperatures of 1290-1850. The observed heat released in the secondary combustion is well correlated with the high explosive and liner heat of combustion with an average efficiency of 54%.