In reply to Phil_Warsaw:
The weather in Scotland can be very changeable. As suggested this can be within one day, or less (I had rain, sleet, flat calm, strong winds, visibility of less than 10 feet and brilliant sunshine in one August day on the Ben) or it can be longer term - days in shorts and T shirts in March and nearly a month's rain in one day in May.
There is generally no problem with water in Scotland. Others might have a different view but provided you are away from civilisation, stream water is safe to drink. In close to forty years I have never had a problem.
Midge hoods are useful but I don't fancy them when walking. DEET based insect repellents are very good but I don't like them - they numb my lips and melt plastic (not good news for glasses, binoculars and cameras). My current favoured one is 'Smidge that Midge'. Not quite as good as DEET based ones but still effective and with none of the nasty effects.
Dave