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The Sea has a profound effect on the weather for two main reasons, firstly because the farthest point you can be away from the sea anywhere in Scotland is about 50 miles. Secondly because of a current called the 'Gulf Stream' or 'Mid Atlantic Drift'. This is a stream of warm water that begins in the Gulf of Mexico, travels across the Atlantic Ocean and then washes on the west coast of the UK. Generally making the west of Scotland milder and wetter than the east coast; indeed it is not unusual for spring to arrive in the west coast two weeks before it arrives in the east coast area. This warm influence means that our temperatures are much warmer than they should be for our northern latitude. For example, Glasgow is on the same latitude as Moscow but our temperatures are much higher in winter. The River Clyde which flows through Glasgow is at about the same latitude as the St. Lawrence in Canada which freezes every year. The River Clyde only froze a few times during the whole of the Twentieth Century and then it was big news in Scotland, because it was so unusual. The Gulf Stream not only brings mild temperatures it also brings rain - lots of rain. Unlike most countries, most of the rain in Scotland falls in the winter ( about five / eights of the annual total ), but if you visit Scotland in the summer you could be forgiven for thinking that most of the rain falls then - because we can get a lot of wet weather at any time of the year. The bigger storm clouds over Scotland can contain as much as 100,000 tons of water and be 5 times higher than our highest mountain Ben Nevis (1343 m / 4,406 ft).
If you've ever carried a basin or bucket of water any distance you will know just how heavy water is. As I watch a downpour I often find myself wondering, 'How do you suspend the enormous weight of 100,000 tons in the air ?' 'How could you move 100,000 tons even a little ?' Our weather system not only floats this great weight in the atmosphere but keeps it suspended while moving it thousands of miles, perhaps from the Canadian Rockies, across the Atlantic Ocean all the way to Scotland. Even then only one water droplet in five will ever fall to earth as rain, but it rains somewhere in the Western highlands ( though thankfully not over the whole area ) - 2 out of every 3 days. Giving Scotland enough rain in a year to fill Loch Lomond ( Britain's largest freshwater lake ) - 15 times over. But look on the bright side - our cousins in western Norway get more rain than the Scots.
Benefits of the large rainfall include the air being cleaned of dust and pollen particles, the lush vegetation ( just look at the colour of the grasses in our photographs even although they were taken in Autumn ), and the spectacular rivers, lochs ( lakes ) and waterfalls. The rain also gives clean, renewable, hydro power to Scotland - generating one tenth of all our electricity supplies. Few countries can have such refreshing drinkable water - strait from the kitchen tap. Scots have been genetically engineered over thousands of years to flourish in this damp moderate cold climate and are perhaps not the best nation in the world to be able to take the merciless Sun in other climates. One study found that most people who develop skin cancer from exposure to the Sun in Australia - were of Scottish descent.
Our weather system means that Scotland is often clouded with the |  landscape | of the West Highland Way receiving about 1,100 hours of sunshine per year. Rainfall occurs on over 250 days per year with over 3,000 mm of rain falling annually in the western Highlands. The area around the start of the WHW, up to about the start of Loch Lomond has an average rainfall of 1000mm [ 40 inches ], by the northern head of Loch Lomond the average rainfall has doubled to 2000mm [ 80 inches ] and by the time Glen Coe has been reached the annual average stands at about 3000mm [ 100 inches ]. In the more sheltered valley regions such as Kinlochleven and Fort William, the annual average rainfall drops to about the same level as the northern area of Loch Lomond. At the southern end of the WHW Glasgow receives about 10 days of gales a year, while the Fort William area receives about 50 days of gales annually.
Unlike North America, mainland Europe etc we do not get the extremes of 'Continental Weather', our climate is
much more moderate, but very changeable within those moderate limits. There are relatively few thunderstorms in Scotland, only about 10 days annually, though this varies slightly from year to year, with most occurring in mid-summer and inland Scotland receiving twice the number that coastal regions receive.
Scotland like every other country is suffering from weather changes due to global warming, making it difficult to accurately speak of average conditions. As an example; in 2002 every Scottish river broke its high water level record. Although there is a certain unpredictability about detailed weather patterns, the overall picture remains broadly accurate. As a rough guide, taking into consideration the recent changes due to global warming, we can say that July normally has the highest temperatures, August is the wettest month of the summer and April, May and June are in an average year the driest months, receiving between them about 20% of the annual rainfall. September is a mild month with moderate levels of sunshine and the risk of larger temperature drops in the evening and early morning, as well as having the risk of chilling strong winds and fairly high rainfall. Below are the average figures for both rainfall and temperatures over the last 125 years in Glasgow ( the start of the WHW ), and in | Fort William | ( the end of the WHW ).
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West - 5% to 10%. North West - 10%. East - 10% to 15%. North East - 15% to 20%.