Extreme heat poses significant risks to public health, particularly for vulnerable populations such as the elderly, children, and those without access to cooling or hydration. During 'Major' (Red) and 'Extreme' (Magenta) HeatRisk levels, the entire population is at risk due to prolonged high temperatures and minimal overnight relief. Emergency room visits and heat-related emergency calls spike during these periods, as observed in Maricopa County and Phoenix Fire Department data. Even on 'Low' risk days, sensitive groups may experience heat-related illnesses, underscoring the need for vigilance and precaution.