Dartmoor - Climate

Climate

Along with the rest of South West England, Dartmoor has a temperate climate which is generally wetter and milder than locations at similar height in the rest of England. At Princetown, near the centre of the moor at a height of 453 metres (1,486 ft), January and February are the coldest months with mean minimum temperatures around 1 °C (34 °F). July and August are the warmest months with mean daily maxima not reaching 18 °C (64 °F). Compared with Teignmouth, which is on the coast about 22 miles (35 km) to the east, the average maximum and minimum temperatures are 3.0 °C and 2.6 °C lower respectively, and frost is at least five times as frequent. On the highest ground, in the north of the moor, the growing season is less than 175 days - this contrasts with some 300 days along most of the south coast of the county.

Rainfall tends to be associated with Atlantic depressions or with convection. In summer, convection caused by solar surface heating sometimes forms shower clouds and a large proportion of rainfall falls from showers and thunderstorms at this time of year. The wettest months are November and December and on the highest parts of the moor the average annual total rainfall is over 2000 mm (about 80 in). This compares with less than 800 mm (31.5 in) in the lower land to the east around the Exe Estuary, which is in the rain shadow of the moor.

Between 1961 and 1990 Met Office data shows that there was an average of 20 days when snow fell on the moor, and over 40 days a year with hail, which is as high as anywhere else in the country. This results when cold polar maritime air that has travelled over a large expanse of warmer ocean is forced to rise over high country.

When average temperatures at Princetown between 1961 and 2000 are compared, the average annual temperature in the decade 1990–2000 was up by 0.2 °C, and the late winter temperature increased by 0.5 °C.