Seasons, Festivals & Events
If school holidays don't restrict you to visiting during Scotland's peak June–August season, then visit in September or May. The weather then is often almost as good and there will be fewer other visitors to contend with, making accommodation easier to find and cheaper too.
That said, Edinburgh's August festivals and it's Hogmanay New Year celebrations shouldn't be missed if you can make them.
Climate
No-one comes to Scotland for the weather, particularly since it's famously unpredictable.
Average temperatures in any city never rise above 18ºC (65ºF) or drop below 5ºC (41ºF). Of course the mercury can go well above or below these points, but it's generally rare to see anything much higher than 25ºC (77ºF/) or lower than about 0ºC (32ºF).
More predictable is the variation around the country: the west is at least twice (in some months four-times) rainier than the east; and the temperature in the hills is always lower, typically around 1ºC (approx. 2ºF) colder for every 100 meters (328ft) you climb.
Festivals & Events