A system, and computer usable program product for discovering thermal relationships in a data processing environment are provided in the illustrative embodiments. An output temperature of a cooling unit operating in the data processing environment is changed from a previous output temperature to a new output temperature. The difference between the previous and the new output temperatures is a change in the output temperature. A change in an ambient temperature proximate to a data processing system is measured. The change in the ambient temperature is a difference between a previous ambient temperature and a new ambient temperature. An expression that represents a relationship between the change in the output temperature and corresponding change in the ambient temperature is determined. The expression is used to determine a cooling correspondence between the cooling unit and the data processing system.