Cairngorms National Park in January

May through September gives you the best weather odds, but each season has its perks and problems. May and June are ideal — long daylight hours (sunrise at 4:30am, sunset after 9pm), fewer crowds, and the dreaded midges haven't arrived yet. Wildflowers carpet the lower slopes and the weather's generally stable. July and August bring peak tourist season. The weather's warmest but also the most unpredictable. Midges are at their worst in still, humid conditions — they can make outdoor dining impossible. Book accommodation well ahead. September is many locals' favorite month. Crowds thin out, the autumn colors are spectacular, and you get crisp, clear days perfect for photography. The stags are rutting too, making for dramatic wildlife encounters. Winter (December-March) transforms the park into a snow-covered wilderness. It's beautiful but dangerous — many trails become technical mountaineering routes. The Lecht and Cairn Gorm ski areas operate when there's enough snow. Avoid October and November unless you enjoy horizontal rain and 4pm sunsets.