This paper describes the thermal profile of a high-performance computing cluster located in two different data centers with quite different thermal profiles. The high-performance advanced simulation and computing (ASC) cluster, code named ASC Purple, is the world’s third fastest supercomputer (Top 500 Supercomputer Sites, http://www.top500.org/), operating at a peak performance of 77.8 TFlop/s. It contains more than 12,000 processors, 50 terabytes of memory, and 2 petabytes of globally accessible disk space. The cluster was first tested in the manufacturer’s development laboratory in Poughkeepsie, New York, and then shipped to a national laboratory in California, where it was installed to support our national security mission. Detailed measurements were taken in both data centers of electronic equipment power usage, perforated floor tile airflow, cable cutout airflow, computer room air-conditioning (CRAC) airflow, and electronic equipment inlet air temperatures. In addition to these measurements, the physical features of the data center were recorded. Results showed that heat fluxes of 700 W/ft2 (7535 W/m2) could be achieved while still maintaining rack inlet air temperatures within specifications. However, in some areas of the Poughkeepsie data center, there were zones that did exceed the equipment inlet air temperature specifications by a significant amount. These areas will be highlighted and reasons will be given for why these areas failed to meet the criteria. Those areas of the cluster in Poughkeepsie that did not meet the temperature criteria were well within the temperature limits at the California installation. Based on the results from these two data centers, necessary and sufficient criteria are outlined for IT racks to achieve inlet air temperatures that meet the manufacturers’ temperature specifications.