The Tees-Exe line is a line of geological demarcation in England that runs more or less directly between Exmouth, Devon, in the south-west, to the mouth of the River Tees on the north-east coast of the country. It divides the generally sedimentary south-east lowlands from the predominately igneous and metamorphic rocks of the more mountainous west and north-west.
This difference in general topography partly accounts for the discrepancy in rainfall between the “regions” with the hilly west having heavier and more frequent precipitation.