This work analyzes the temperature effects on microwave circuits by employing a novel field-circuit hybrid multiphysics simulation. Firstly, the multiphysics simulation is implemented by solving the coupled governing equations including Poisson equations, semiconductor transport equations, and thermodynamic equations; then, the multiphysics simulation is incorporated into circuit analysis; finally, the circuit simulation results are integrated into the finite-difference time-domain (FDTD) simulation by equivalent sources. In this manner, a field-circuit hybrid multiphysics simulation method is presented. Taking two different microwave rectifiers operating at S- and C-band as examples, temperature effects are analyzed by the proposed approach. Simulation results are in good agreement with measured values, demonstrating the accuracy and applicability of the proposed approach. The presented method more suitably reveals the temperature effects on the rectifier.