In July 1995 Chicago endured one of the deadliest heat waves in U.S. history. Over the course of several days of extreme heat and high humidity, the city recorded a substantial and sudden increase in deaths attributed to heat-related causes. The mortality spike disproportionately affected elderly residents, low-income neighborhoods, and people living alone or without access to cooling. The heat wave occurred in a context of prolonged hot weather across the region. Daytime temperatures climbed into the 90s and early 100s Fahrenheit, while overnight lows remained unusually high, preventing relief. High humidity made conditions more dangerous by reducing the body’s ability to cool itself through sweating. Power outages in some neighborhoods and limited access to air conditioning compounded risks for vulnerable populations. Public-health officials and researchers later identified several factors that contributed to the high death toll. Many deceased individuals lived in buildings without functional air conditioning, and some could not afford to run whatever cooling they had. Social isolation played a critical role: those who died were often elderly and lived alone, with limited contact from family, neighbors, or social services. Language barriers, fear of authorities, and lack of awareness about the seriousness of heat-related illness were also reported as impediments to seeking help. The city’s emergency response and preparedness systems were scrutinized after the crisis. Officials and community advocates pointed to shortcomings in outreach to vulnerable populations and delays in mobilizing cooling centers and other protective measures. Municipal and non-profit efforts to check on isolated residents were described as uneven and insufficient in the face of an escalating emergency. In the aftermath, Chicago and other jurisdictions re-examined heat emergency plans. Measures taken in subsequent years included expanding public cooling centers, improving communication about heat risks in multiple languages, coordinating welfare checks for isolated elders, and integrating heat response into broader emergency-management and public-health strategies. Researchers also emphasized the need to address underlying social determinants—such as housing quality, poverty, and social isolation—that increase vulnerability to extreme heat. Scholarly and governmental investigations of the 1995 event contributed to a deeper understanding of urban heat vulnerability. Public-health studies used mortality data to estimate excess deaths attributable to the heat wave and to map spatial patterns showing higher impacts in poorer neighborhoods. These findings informed policies aimed at reducing future heat-related mortality, including infrastructure upgrades, targeted outreach, and surveillance systems to detect spikes in heat-related illness and deaths. While the 1995 Chicago heat wave remains a frequently cited example of the lethal potential of extreme heat in cities, it also served as a catalyst for policy changes and community-based efforts intended to reduce the human toll of future events. Ongoing research and municipal planning continue to address heat risks, particularly as climate change increases the frequency and intensity of extreme-heat episodes.