This paper describes an experimental study in which a hot air jet is discharged from a 25 mm nozzle at the centre of the top surface of a cuboid placed on the floor of a wind tunnel. The cuboid has a cross section of 0.2 m × 0.2 m and a length of 0.4 m. A 12.7 µm fine-wire thermocouple has been used to measure the unsteady temperatures within the jet plume as it is swept downstream by the cross-flow. Dimensional analysis indicates that the trajectory and temperatures within the plume are momentum-dominated and are governed by the jet to cross-flow momentum flux ratio. Three different jet temperatures and velocities were therefore selected to give a constant momentum flux ratio and the similarity of the normalised temperature profiles downstream of the jet nozzle confirmed the dimensional analysis. The study being reported is part of a larger project to investigate the dispersion of hot engine exhaust gases from a ship's engines, and how they interact with the ship's helicopter. The experimental results from the generic bluff-body geometry of a cuboid will be compared with the results from an unsteady Computational Fluid Dynamics (CFD) analysis to provide confidence in the CFD methodology that will then be applied to the full-scale ship. The temperature measurements presented in the paper have been compared with a preliminary steady-state CFD analysis with encouraging results.