Tees River Valley (England)

Teesdale is a dale, or valley, located principally in County Durham, North East England. It is one of the Durham Dales, which are themselves part of the North Pennines, the northernmost part of the Pennine uplands. The dale is named after its principal river, the Tees, which has its source below Cross Fell (890 m (2,930 ft)) in Cumbria. The upper dale is remote and high, but becomes gentler after it enters County Durham shortly downstream. The dale follows the river's south-easterly course to Barnard Castle, at which point the landscape begins to flatten into the Tees Lowlands. The Cumbrian part of Teesdale was historically divided between Cumberland and Westmorland, and the County Durham area between the former and Yorkshire. Large parts of Teesdale are within the North Pennines national landscape, and Upper Teesdale has been designated a Site of Special Scientific Interest. Parts of the local climate have been scientifically classified as "Sub-Arctic", and snow has sometimes lain on Cross Fell into June.