Museum, London. Records of flowering plants include Dactylorhiza purpurella (Stephenson and Stephenson) Soó. Climate The majority of Donegal has a temperate oceanic climate (Köppen climate classification: Cfb), with upland areas in the Derryveagh and Blue Stack ranges classified as oceanic subpolar (Köppen climate classification: Cfc). The county's climate is heavily influenced by the North Atlantic Current. Due to the topography of western Donegal, it receives orographic rainfall, where the air is forced to rise on contact with its mountainous coastline and subsequently cools and condenses, forming clouds. The mountains of Donegal are among the cloudiest places in Ireland, and northern Donegal is the windiest. Irish monthly record wind speeds for March, June, July, September, November and December have all been set at Malin Head. The highest wind speed ever recorded in Donegal was 181 km/h (112 mph) on 16 September 1961, during Hurricane Debbie. The Atlantic ocean has a significant cooling effect and, due to the county's long, thin shape and punctuated coastline, nowhere in Donegal is particularly far from the ocean, giving it a generally cooler climate that is more similar to western Scotland than the rest of Ireland. The average maximum temperature in July at Malin Head is just . However, due to its exposed coastal location, the climate at Malin Head is not representative of most of the county. Winds are much lighter in the county's interior and temperatures are cooler in the winter and warmer in the summer. Annual rainfall in the county ranges from around in the lowlands of north-eastern Donegal to over in western mountainous areas. Precipitation exceeding 1 mm (0.04 in) will fall across all areas of Donegal on over 150 days per year. While the prevailing wind direction in Ireland is south-westerly, which brings warm, moist air from the Gulf of Mexico, a low-pressure Polar front regularly passes to the northwest of the island, bringing cold and unsettled weather to the region. The upland areas of Donegal will reliably receive some covering of snow every year. In lowland areas, snow - while still relatively infrequent - is more common than in the rest of Ireland. Despite its coastal location, Malin Head records an average of 20 days of snowfall per year. In contrast Valentia Island, a similarly placed coastal station in the southwest of Ireland records just 3. Geology and terrain Donegal can be divided into six main geological subdivisions. Of these,