This research delves into the critical domain of high-temperature pressure vessel design, focusing on SA 387 Grade 11 Class 2 steel—an exceptional material known for its resistance to both corrosion and high temperatures. The study combines experimental investigations and numerical simulations to explore the intricate temperature distributions within this material during the Submerged Arc Welding (SAW) process. Experimental endeavors entailed welding SA387 steel plates under controlled conditions, precisely measuring temperatures at key locations. Concurrently, a numerical finite element analysis (FEA) model was developed, incorporating a 3D Goldak’s double ellipsoidal heat source model within ANSYS software. The research seamlessly integrates these two approaches, allowing for a comprehensive comparison of experimental and numerical temperature data. The results highlight the capacity of the FEA model to predict temperature profiles during SAW accurately, presenting a potent tool for optimizing welding parameters without extensive trial and error. Furthermore, this study advances our comprehension of welding processes involving high-temperature-resistant materials, offering valuable insights for industries requiring operations at elevated temperatures.