The Scottish weather can be changeable and is often very localised. This means that you may well have a morning of rain and an afternoon of sunshine - and that the weather may be quite different 10 miles away in the next valley. Remember this when getting a forecast.
Cool days in summer: 10 - 15° C (50 - 60° F).It is a good idea to take layers of clothing with you each day and to change whenever the temperature does. As a general rule, always take rain gear with you and remember that the higher you go, the cooler it gets. For every 150 metres of vertical ascent, the temperature drops about 1° C. (This ratio varies depending on the humidity level in the air - in wet weather the rate at which it gets colder with altitude increases, so even if it is quite warm on the valley floor it can be much colder on the mountain tops, and that's without taking into account the wind-chill factor which can also be considerable). But on our routes there are no high altitude sections (except if you are planning to climb Ben Nevis if you are passing through Fort William) so don't worry about this.
Seasons - the best time to come to Scotland
Traditionally the peak season for visiting Scotland is in July and August, but don't be put off coming to Scotland earlier or later in the year, as the weather can be just as good if not better. The chances are that over a week or so in Scotland the weather will be varied, with some good and some not so good days, no matter what the time of the year. Another point to remember is that while it does rain in Scotland, it is not as bad as some people make out - Edinburgh has the same average annual rainfall as Rome. That said, it is generally wetter on the west coast than the east, but in recent years the west coast has had some excellent spring & early summers.
January & February. These months are traditionally cold and unpleasant. Aside from 1994-95 and 2000-01, the winters throughout the 1990s and early 2000s have not been fairly mild and most years we have had more rain than snow. But both 2008-09 and 2009-10 (so far) have been cold winters and much more like those of the early 1980s, with minimum temperatures of -15°C at night not being uncommon. Temperatures are not the only factor however, as moist air at 0°C can feel just as cold as dry air at -10°C, especially if it is windy. Regardless of the humidity, temperatures and wind chill, the hours of daylight are still very short in these months so they aren't the best for a walking holiday.
March. This is really still winter in Scotland, but if you are hardy and prepared for potentially grim weather there's no reason why you shouldn't come to Scotland. Like January and February be prepared though, and unless you want some ice-climbing on Ben Nevis or Glencoe try to aim for a time later in the year. If you do plan on walking or climbing in the Scottish mountains do check SportScotland's Avalanche and Snow Information Service beforehand.
In April & May the days are lengthening and there can be some excellent spells of spring sunshine. There is considerable range in the conditions over these two months; its not unknown for there to be some late low-level snow falls in April, and yet within a week or two the sunshine can have a summer feel to it. It can also be variable on a daily basis - you may experience rain, snow and sunshine all in the same day - which can add interest to the scenery and your walk. There is usually a good spell of high pressure in April, which lasts a week or so and brings sunny & warm weather to the whole country. These months are said to be best for hill-walking, as the snow-capped mountains look their best in the blue skies and spring sunshine.
June is traditionally the best month to visit Scotland for weather - and the month when the days are longest - in some parts of Scotland you can still read a newspaper outside at midnight. There is usually a cold week in early June, but then it warms up so that the average midday temperature is about 15-20°C (60-70°F). As the days are long, it can get hot inland, but very rarely above 28°C in the shade. The sun can burn too - a hat and sunglasses are strongly advised. (This applies from April onwards). De-hydration and heat stroke (not commonly seen as a likely outcome of walking in Scotland) can be a problem if you are walking all day without adequate drinks.
July & August. If you are coming to Scotland in July and want to avoid the peak season try to come in the first two weeks of the month - before the English school holidays start. Even so, the vast majority of tourists never leave the carparks and main centres, so, other than on the West Highland Way, the paths and trails you follow are never very busy. The weather is usually fine in these months. By this time the rivers and lochs are at their warmest (though some are warmer than others) if you want to go outdoor swimming.
September. The weather in this month is not as hot as July or August, but is usually fine and probably more comfortable for walking. The trees begin to turn to their autumn colours later in the month, and although the weather can be variable, September is still a good month to come to Scotland. The days are getting shorter however - sunset time is about 7.30pm in the middle of the month.
October. The autumn colours are usually at their best in October, but the weather in this month can be cold and wet, and the days get progressively shorter (the sun sets about 6pm by the end of the month). For these reasons we don't advise you to take your walking holiday in Scotland after the first or second week of this month.
November & December. These months are characterised by short days, and usually cold and wet weather. Rain at sea level usually falls as snow on the mountains, but in milder winters there usually isn't much snow until after Christmas or New Year. But the trees are still bare and there is little colour in the landscape - not the best time to come to Scotland.