This paper reports on a field study of personal exposures to summer heat stress in Elizabeth, NJ, USA, a medium-sized city that hosts an international airport, a shipping port, a petrochemical refinery complex, and a major transportation corridor in a densely populated metropolitan area. The study deploys a network of fixed outdoor sensors, a network of fixed indoor sensors, and mobile personal exposure monitors that are carried by residents. Study participants live in buildings operated by a public housing authority and include elderly retirees, high-school children, and working-aged people. Results show that residents’ measured personal exposures to extreme heat are much lower than measurement of ambient conditions might suggest. Resident time allocation toward cooler, indoor activities explains much of the difference between ambient conditions and personal heat exposure. Individuals show that they adapt to changing environmental conditions, within constraints afforded by the built environment. This paper presents the Exposure Duration Curve as a useful graphical device for comparing the intensity and duration of environmental exposures.