Objective: to explore how temperature variations influence ultrasonic vibration attenuation in rail steel. To propose a methodology for evaluating thermal stresses in continuous welded rails by analyzing the amplitude variations of ultrasonic signals transmitted through the rail structure. Methods: the theoretical fundamental principles governing the propagation of ultrasonic waves were examined, with a specific focus on how rail temperature conditions impact on the ultrasonic signal amplitude. Field measurements were carried out to verify the theoretical data. Results: a distinct correlation has been established between the rail temperature and the attenuation of ultrasonic vibrations transmitted through the rail. A mathematical expression describing the dependence of ultrasound amplitude on the temperature of the rail steel has been obtained. The study has identified specific variables that could compromise measurement precision. The data demonstrates that integrating temperature-dependent variables into ultrasonic amplitude analysis is crucial for enhancing the precision of current methods used to estimate thermal stresses in continuous welded rail systems. Practical significance: the findings of the study will allow the development of more accurate and reliable methods for monitoring thermal stresses in continuous welded rail tracks, and can be used to improve existing techniques for detecting thermal stresses in continuous welded rails.