I have experienced 4 seasons in one day in Snowdonia, the Lake District and several areas of Scotland (not just the Cairngorms). Weather is hard to predict in this area of Scotland. I have seen it be almost 20 C in January and freezing cold in the middle of the year. Rain is never too far away in the Scottish hills. A useful weather forecasting tip is: If you cannot see the tops of the hills, it is raining. If you can see the tops of the hills, it is going to rain. At that time of year, if it is not raining the midges will be out looking for blood, but he Cairngorms are pretty windy and that can be a help. As we have only 2 seasons (light winter and dark winter) it is best to come prepared for all weathers. You won’t need so much insulation at this time.