Introduction: This study aimed to identify climatic and environmental factors influencing the occurrence of heatstroke. Methods: A systematic review was conducted in February 2020 and 428 potentially relevant records were searched among PubMed, Scopus, Science Direct, and Web of Science and Google scholar databases in English language. After quality assessment and cross-checking by two independent researchers, finally, 14 articles included in this systematic review. Results: Solar radiant heat, ambient temperature, humidity, maximum and minimum daily temperature and humidity, water vapor pressure, wet bulb globe temperature (WBGT) index, Heat index (HI), sub-tropical climate, heatwaves, Urban Heat Island (UHI) effect, urbanization, daytime population density, surface temperature, high activity level in indoor/outdoor settings and local ambient temperatures were positive correlated factors of exertional heat illnesses (EHI) and exertional heat stroke (EHS) incidence and mortality. Seasonal acclimation, vegetative cover, cool roofs, tree canopy cover, cloud cover, wind speed and shading were inversely related factors of EHI and EHS. Conclusion: According to the results of the study, in order to prevent the increase of heat-related illnesses, it is necessary to consider and strengthen the factors affecting the reduction of the incidence of EHI and EHS, which were identified as negative correlated factors in this study.