Teesdale is a dale, or valley, of the east side of the Pennines in County Durham, England. Large parts of Teesdale fall within the North Pennines Area of Outstanding Natural Beauty (AONB) - the second largest AONB in England and Wales. The River Tees rises below Cross Fell, the highest hill in the Pennines at , and its uppermost valley is remote and high. The local climate was scientifically classified as Sub-Arctic and snow has sometimes lain on Cross Fell into June (there is an alpine ski area Yad Moss).