1-D FDTD solvers are being developed to simulate multiphysics problems seen in real world applications. These simulators are attempting to solve self-consistently the Maxwell, heat conduction and thermoelasticity equations in the time domain and determine the impact of thermal variations on electromagnetic performance, e.g., the reflection and transmission coefficients of a periodic structure. The solvers are being used to study two main situations: 1) EM emission control by thermally heating a periodic structure and the change in this emission control when changes in material properties and physical dimensions of the structure occur. 2) EM performance degradation caused by the heating from the material losses and the associated dimensional changes in the periodic structure. The results from this study lay the basis for advancing to 2-D and 3-D solvers that can be used to study antennas in extreme environments like missile flights and space environments.