Summer heat in the Valley of the Sun is almost legendary with temperatures soaring well above 100 degrees Fahrenheit. However, the impact of this heat on people is variable across the Valley. Poor neighborhoods with sparse vegetation and a preponderance of asphalt and concrete surfaces suffer the most while higher-income neighborhoods with lush, mesic vegetation can be several degrees cooler. CAP scientist Sharon Harlan and a team of faculty and students are investigating human vulnerability to urban heat through a CAP-leveraged and National Science Foundation-funded project, Urban Vulnerability to Climate Change. Building on results from the Phoenix Area Social Survey and a previous grant, this initiative will provide important insights into understanding climate vulnerability at a metropolitan scale. As a recent article in The Arizona Republic indicates, urban heat is a critical public health issue in the Valley.