The relationship between the transient, meridional eddy sensible heat and latent heat fluxes during January and July at 850 mbar is examined using band-pass-filtered, European Center for Medium-Range Weather Forecasts data for the period 1979--1989. The fluxes are shown to be strongly positively correlated both temporally and spatially. They are most strongly correlated in the the midlatitude storm tracks, and this relationship varies from January to July and from the northern to the southern hemisphere. The climatic variables that affect this relationship are the local temperature gradient, moisture availability and land/sea distribution. The temperature gradient is the most important influence, such that the relationship is strongest when the temperature gradient in the storm track is strong and advection by the meridional wind is strong. When the gradient weakens, moisture availability and the distribution of land and sea exert a greater influence upon the fluxes, and the relationship between them is weaker.¿ 1997 American Geophysical Union