A system capable of both increasing warm day output and maintaining compressor operating margin across the ambient and load range of a gas turbine combined cycle installation. The proposed solution takes advantage of the fact that both goals can be satisfied by manipulation of compressor inlet air temperature. Specifically, the system is designed to heat inlet air as may be required to maintain safe compressor operating margin at low ambient air temperatures or when burning dilute fuels. In the alternative, the system is designed to cool inlet air on warm days.