Aberystwyth, at the midpoint of the country's west coast, has nearly 17 hours of daylight at the summer solstice. Daylight at midwinter there falls to just over seven and a half hours. The country's wide geographic variations cause localised differences in sunshine, rainfall and temperature. Average annual coastal temperatures reach and in low lying inland areas, lower. It becomes cooler at higher altitudes; annual temperatures decrease on average approximately each of altitude. Consequently, the higher parts of Snowdonia experience average annual temperatures of . Temperatures in Wales remain higher than would otherwise be expected at its latitude because of the North Atlantic Drift, a branch of the Gulf Stream. The ocean current, bringing warmer water to northerly latitudes, has a similar effect on most of north-west Europe. As well as its influence on Wales' coastal areas, air warmed by the Gulf Stream blows further inland with the prevailing winds. At low elevations, summers tend to be warm and sunny. Average maximum temperatures range between . Winters tend to be fairly wet, but rainfall is rarely excessive and the temperature usually stays above freezing. Spring and autumn feel quite similar and the temperatures tend to stay above – also the average annual daytime temperature. The sunniest time of year tends to be between May and August. The south-western coast is the sunniest part of Wales, averaging over 1700 hours of sunshine annually. Wales' sunniest town is Tenby, Pembrokeshire. The dullest time of year tends to be between November and January. The least sunny areas are the mountains, some parts of which average less than 1200 hours of sunshine annually. The prevailing wind is south-westerly. Coastal areas are the windiest, gales occur most often during winter, on average between 15 and 30 days each year, depending on location. Inland, gales average fewer than six days annually. Rainfall patterns show significant variation. The further west, the higher the expected rainfall; up to 40% more. At low elevations, rain is unpredictable at any time of year, although the showers tend to be shorter in summer. The uplands of Wales have most rain, normally more than 50 days of rain during the winter months (December to February), falling to around 35 rainy days during the summer months (June to August). Annual rainfall in Snowdonia averages between (Blaenau Ffestiniog) and (Snowdon's summit).