A virtual temperature monitoring system in a data center communicates with servers mounted in racks to receive internal temperature data generated by internal temperature sensors of the servers. The system derives a virtual sensor measurement of external temperatures external to the server, including a portion of a cold aisle that extends proximate to a rack in which the server is mounted, based upon a relationship between the received internal temperature sensors and the external environment. Sensor data from other sensors can be received via a building management system, and building management signals to the building management system can be generated based at least partially on the virtual sensor data. The virtual sensor data can be used to generate a graphical representation of the servers that highlights relative thermal characteristics of the servers based on the virtual external sensor measurements, including heat indices, excursions beyond thresholds, historical excursion histories, etc.