Teesdale is a dale, or valley, of the east side of the Pennines in 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 (2,930 feet O.D.) in the Pennines, 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).