A transient numerical investigation using the conjugate heat transfer (CHT) technique has been carried out to evaluate the effects of boundary heat flux on the thermal characteristics due to the turbulent air and water jet impingement process. For the water jet, the volume of fluid method is employed to capture the interface in the multiphase flow. It is found that the wall conduction may alter the prediction of the fluid-solid interfacial thermal characteristics compared with that from a pure convection process. The degree of influence depends on the working fluid, nozzle size, metal thermal conductivity, metal thickness and boundary heat flux. The CHT approach tends to reorganize the uniform heat flux distribution at the boundary to a non-uniform heat flux distribution at the fluid-solid interface. This is mainly attributed to the conjugate effect of the solid. For a given jet Reynolds number and boundary heat flux, the CHT results reveal that the convective heat flux at the stagnation point is higher for the air jet than for the water jet. Contrary to the non-CHT predictions, the interfacial temperature distribution is uniform for metals that possess a higher thermal conductivity with the air jet and for all metals with the water jet. (C) 2017 Elsevier Ltd. All rights reserved.