In July 1995, Chicago experienced a severe heat wave that culminated around July 12–16 and is widely regarded as one of the deadliest heat events in the city’s modern history. Extended high temperatures, combined with high humidity and overnight lows that provided little relief, contributed to a rapid increase in heat-related illness and deaths, particularly among older adults, people with underlying health conditions, and socially isolated residents. Meteorological context A strong high-pressure system settled over the central United States in early July 1995, producing persistent sunny skies, suppressed winds, and prolonged daytime heating. Heat indices reached dangerous levels, and overnight temperatures remained elevated, limiting recovery time for vulnerable populations. Urban heat island effects—where built surfaces retain and re-radiate heat—likely amplified nighttime temperatures in densely built neighborhoods. Human impact and demographics Estimates of excess mortality associated with the July 1995 heat wave vary by study and methodology, but public health analyses identified hundreds of excess deaths in the Chicago area over the event. Many fatalities occurred at home without air conditioning or in poorly ventilated housing. The death toll was unevenly distributed: lower-income neighborhoods, areas with older housing stock, and communities with higher proportions of elderly or socially isolated residents suffered disproportionately. Emergency services and hospitals reported surges in admissions for heat stroke, dehydration, and exacerbations of chronic conditions. Public response and institutional lessons The 1995 heat wave exposed gaps in emergency preparedness, public health outreach, welfare services, and communication to at-risk populations. In its aftermath, city and public health officials reviewed and revised heat response protocols, including more proactive public warnings, expanded cooling center plans, targeted outreach to vulnerable residents, and partnerships with community organizations. The event contributed to the development of heat–health warning systems and municipal heat emergency plans used in subsequent decades. Research and policy legacy Scholars and public health practitioners have studied the 1995 event to understand how extreme heat interacts with social and environmental factors. The incident is often cited in literature on climate adaptation and urban resilience as an early example of how heat disproportionately affects marginalized populations. It also informed later municipal efforts to mitigate urban heat through tree planting, reflective roofing, and heat mapping to prioritize interventions. Uncertainties and sources Counts of heat-related deaths from 1995 differ across reports because of differing definitions (direct heat stroke vs. excess mortality during the period) and data methods. Public health reviews, contemporaneous news reporting, and later academic analyses together provide the basis for the widely accepted characterization of the July 1995 heat wave as unusually deadly for Chicago. No novel or unattributed quotes are used here; the summary synthesizes established historical and public health information about the event. Contemporary relevance As extreme heat events have become more frequent and intense in many regions, the lessons from Chicago’s 1995 heat wave remain relevant for urban planning, public health outreach, and social services. Ensuring access to cooling, reducing urban heat islands, and reaching socially isolated residents are ongoing priorities for reducing heat-related harm.