Dehydration can set in within hours or even as quickly as 30 minutes for those engaging in strenuous outdoor activities. Vulnerable populations, including the elderly, children, and individuals on medications like diuretics or antihistamines, face heightened risks. Heat-related illnesses such as heat exhaustion and heat stroke may accompany dehydration, leading to symptoms like rapid heart rate, low blood pressure, and altered mental status. Prolonged exposure to high temperatures without adequate hydration can result in life-threatening conditions. Humidity exacerbates the situation by preventing sweat evaporation, further impairing the body's cooling mechanisms. (Source: HuffPost)