Meteorologists hate giving weather advice to people holidaying in the UK because our climate is so variable, both from place to place and from year to year. However, one reliable tip is that the best time to visit the highlands and islands of Scotland is May or early-June. This is one time of the year and one part of the country when the climate is at least semi-regular. True, there are still big year-by-year variations, but broadly speaking late spring provides much more reliable sunshine compared with high summer which is often cloudy and drizzly.
The reason is simple. The characteristic sunless, wet weather of western Scotland is a function of the prevailing southwesterly winds which deliver moist air from the Atlantic. This cloudy airflow fails most often during spring, replaced by northerlies and easterlies, and when the wind blows from this quarter places like Fort William, Skye, Mull and Wester Ross are sheltered by the great bulk of the highland massif.
The statistics bear this out. At Duntulm on the Isle of Skye the long-term average sunshine total for May is 201 hours compared with 170 hours in June (when the westerlies often return around mid-month) and just 125 hours when the wind blows relentlessly from the Atlantic in most years. By contrast, along the east coast of Britain both June and July are, on average, sunnier than May. The west coast of Scotland is also almost twice as wet in an average July compared with an average May. Recent days have provided a perfect illustration of the point. At Tiree in the Inner Hebrides the sun shone for 90 hours during the ten-day period from April 28 to May 7, an average of 9 hours per day, compared with just 40 hours at St Helier, Jersey, during the same period. It is not just western Scotland that is favoured during spring northeasterlies. The Lake District, the Lancashire coast, north and west Wales and much of Ireland also enjoy abundant sunshine during this sort of weather pattern.