One embodiment of the present invention provides a system that estimates the relative humidity inside a computer system. During operation, a set of performance parameters of the computer system and an external relative humidity outside of the computer system are monitored. Then, the relative humidity inside the computer system is estimated based on the set of performance parameters, the external relative humidity, and a relative humidity model, wherein training of the relative humidity model includes measuring an external training relative humidity outside of the computer system and a training relative humidity inside the computer system while monitoring the set of performance parameters of the computer system.