The variability of thermoelastic stresses at the Earth's surface is investigated on different scales with a three-dimensional numerical model. Energy transfer by heat conduction and radiation of sun, atmosphere and Earth's surface is regarded. It is shown that thermoelastic stresses are considerably high, so that they are able to assist faulting and thus force weathering of rocks. Their morphological distribution strongly depends on the spatial scale of the relief; on large scales it is governed by the temperature distribution, on small scales (below a few meters) the surface morphology plays the dominant part. ¿ 1999 American Geophysical Union