Background: heat stroke is a preventable severe condition of heat-related illnesses; it is an emergency condition affecting millions of people around the world. Heat related illnesses ranged from mild heat exhaustion to life-threatening heat stroke. Early detection and treatment of heat-related illnesses crucial to avoid mortality and morbidity. The aim of this study was to evaluate awareness of heat illnesses, its symptoms, treatment and prevention among the population of Saudi Arabia.  
Methodology: a cross-sectional study carried out an online survey, Saudi Arabia, between, 1 November 2017 and 23 June 2018. Data were collected by using a valid multiple-choice question (MCQ). Survey questions included the possible thought causes and risk factors of both heat stroke and heat exhaustion.
Result: a total of 865 participants, the majority were Saudi citizens (806). Age and gender were almost equal. 281 were involved in the medical fields. Conclusion: this study assessed the awareness of heat stroke and heat exhaustion among the health staff and medical students in different aspect of heat-related illness (Mainly heat stroke and heat exhaustion) and compared it to the level of awareness of general population in some aspect of heat-related illnesses. Almost, two third of medical personnel differentiate heat stroke definition when it was listed among other heat-related illnesses.in the other hand, knowledge of heat exhaustion definition was markedly lower among both health staff and non-health staff.44.6% of the participants chose all cooling methods as appropriate treatment of heat stroke. 71.1% knows that heat stroke had more devastating outcomes if not managed properly and rapidly than heat exhaustion.34% of the medical personnel thought avoiding hot spots was the best way to prevent heat-related illnesses; a similar number of the non-medical (31%) also thought the same.  Awareness of heat-related illnesses and differentiation between them in relation to the definition, sign, symptoms, diagnosis, and treatment is not satisfactory.