As an air mass is advected from a heated land surface over a cooler sea, it is extensively modified by the underlying surface with the subsequent formation of a stably stratified internal boundary layer (SIBL). Due to weak turbulence, changes in surface forcing are communicated very slowly across the depth of the SIBL and its growth rate cannot be described in terms of local parameters. Therefore, it has been proposed that the growth of the SIBL is controlled by the fetch integrated value of surface heat flux. This approach is adopted in the present paper in order to develop a simple equation capable to describe the development of the SIBL as a function of downwind distance and external forcings, such as pressure gradient force, surface roughness and potential temperature difference between sea and land surface. The derived relationship is tested against a limited data set from the ¿resund experiment. ¿ 1998 American Geophysical Union