Continued growth in the American Southwest depends on the reliable delivery of services by critical infrastructure systems, including water, power, and transportation. As these systems age, they are increasingly vulnerable to extreme heat events that both increase infrastructure demands and reveal complex interdependencies that amplify stressors. While the traditional analytic approach to preparing for such hazards is risk analysis, the experience of Hurricane Katrina provides a warning of the limitations of risk-based approaches for confronting complexity, and the potential scale and impact that can result from cascading failures under extreme stress. By contrast, this research is the first to apply resilience theory to understanding complex infrastructure interdependencies during an extreme heat event in Phoenix, AZ and the role of sensing, anticipating, adapting, and learning (SAAL) for mitigating catastrophe.