The potential of time-resolved coherent anti-Stokes Raman scattering (CARS) for thermometry studies in combustion processes using the isotropic Q-branch of nitrogen is discussed. Despite the increasing complexity of the femtosecond (fs)-CARS transients with rising temperature, due to the high number of contributing levels, the time-resolved CARS signal can be simulated with excellent correspondence to the experiment. The feasibility of flame thermometry with fs-CARS is demonstrated for an atmospheric pressure methane/air flame.