is the coldest time of the year with an average maximum of 5.8 degrees Celsius. July is usually the warmest month with an average maximum of 19.4 degrees Celsius. Average annual rainfall is with rain falling on 129 days. Geology The site of the post glacial Lake Pickering, the vale has a predominantly level topography covered by glacial drift deposits, with some rolling low ground on boulder clay and moraines in the far east. The underlying Jurassic sandstones and mudstones have little direct influence upon the landscape. There are minor outliers of Jurassic limestone in places at the foot of the Howardian Hills and the North York Moors, and there is some eroded chalk from the Wolds mixed with sands at the base of the Wolds in the southeast. There are springs associated with calcareous aquifers in places on the periphery of the vale. Drainage The Vale of Pickering is a drainage basin for the surrounding hills. At the eastern end of the area the canalised and straightened River Hertford drains west into the Derwent, which rises on the North York Moors a few miles from Scarborough before draining southwards into the vale. At the western part of the area the River Rye and its numerous tributaries flow eastwards and join the Derwent to the north of Malton. The Derwent then flows southwards through Malton and the Kirkham gorge to eventually join the River Ouse at Barmby on the Marsh. Many of the watercourses in the Vale are maintained by the Vale of Pickering Internal Drainage Board. Natural history Following the last glaciation Lake Pickering gradually drained away leaving a complex of rivers and marshes. The carrs, marshes, ings and wet meadows have now all been drained by humans and, as well as the rivers, the landscape is crossed by a network of canalised drainage ditches and canals which regulate the water table. In spite of this legacy of river engineering and land drainage the rivers of the Vale of Pickering remain one of the most important wildlife features of the area. There are many species of aquatic birds, plants insects and mammals inhabiting the riparian areas and greyling and brown trout fish thrive in the rivers of the western area. The deep-sided drains that are managed by frequent dredging and contaminated by agricultural run off are poor habitats for wildlife. Drainage has created reasonably fertile soils, which are used