Chemical, biological, radiological, and nuclear (CBRN) military teams face extreme conditions due to the hazardous nature of their work and the characteristics of personal protective equipment, which can cause a rapid and dangerous increase in vital physiological parameters in hot climates. This study investigated the physiological impact of personal protective equipment in distinct thermal environments (high vs ambient). A sample of Military Academy students, with characteristics similar to members of CBRN teams, performed a 30 min physical protocol while wearing personal protective equipment. The primary aim was to analyse the variation of physiological parameters (core temperature, skin temperature, and heart rate) and subjective perceptions of thermal stress (thermal sensation, thermal comfort, perception of skin moisture, and rate of perceived exertion) in military personnel. The data was analysed using various descriptive statistical methods, combined with adequate statistical inference techniques considering non-parametric statistical methods for hypothesis testing development. The results demonstrated that personal protective equipment use exacerbates thermal strain, particularly in hot environments, leading to increased core and skin temperatures, as well as heart rate. The perception of thermal discomfort and skin moisture also increased in warmer conditions. Particularly, male participants tended to report feeling warmer, less comfortable, and experiencing more skin moisture at ambient temperature compared to females. It is concluded that understanding the impact of personal protective equipment under varying thermal conditions is crucial for preventing adverse clinical situations and optimizing the safety and performance of military personnel in risk scenarios. The implemented protocol may also be valuable in assessing the adaptability to different environments in admission tests for CBRN teams.