The escalating occurrence of extreme high temperature weather exposes individuals to passive heat stress more frequently, resulting in strain on the vascular system. One example of this strain is the doubling of cardiac output during heat stress, achieved through an increase in heart rate and the redirection of blood flow from non-cutaneous tissues. These combined stressors can present substantial risks, potentially leading to syncope and cardiovascular collapse. This review aims to provide a comprehensive overview of the principal cardiovascular responses to passive heat stress, with a specific focus on the cellular and molecular reactions of blood vessels to passive heat stress, to facilitate the formulation of treatment guidelines and preventive measures to mitigate risks associated with the escalating occurrence of severe heat events. Furthermore, in addition to its function as an environmental stressor, mild passive heat stress is also acknowledged as a therapeutic intervention for enhancing or ameliorating deteriorations in vascular wellbeing. Consequently, passive heat stress assumes dual roles with potential benefits and drawbacks in relation to vascular health, necessitating further investigation to comprehensively grasp the ramifications of heat intensity on vascular reactions and ascertain the most effective strategy for managing heat stress in susceptible populations. Importantly, the vascular consequences of passive heat stress are highly dependent on the intensity, duration, and frequency of heat exposure, with moderate thermal stimulation promoting adaptive vascular remodeling whereas excessive heat exposure may lead to endothelial injury, circulatory dysfunction, and multiple-organ damage. A better understanding of these context-dependent vascular responses may facilitate the development of evidence-based thermal interventions and improve prevention strategies for heat-related cardiovascular complications, particularly in vulnerable populations such as older adults and individuals with cardiometabolic diseases.