Late spring to early autumn (May to September) is the prime season, with warm days, green hills, running lake boats and open mountain railways, though July and August bring peak crowds and prices. Spring and autumn are quieter and pleasant, while winter is cold and often grey in the city but opens up snow and skiing on nearby Pilatus, Rigi and the wider Alps.
Switzerland is one of the most expensive countries in the world, and Lucerne is no exception. The main risk to your trip is your budget rather than your safety, so plan for costly food, drinks and mountain excursions, and use lunch menus, supermarkets and rail passes to keep spending in check.
Weather on Pilatus and Rigi can change fast and differ sharply from the mild city below, with cloud, cold and even summer snow at altitude. Check the mountain webcams and forecast before heading up, bring warm layers and sturdy shoes, and confirm that seasonal railways and cable cars are running.
Lake Lucerne is beautiful for swimming in summer but the water stays cold and deep, with sudden drop-offs and boat traffic. Swim only in marked bathing areas, keep well clear of shipping lanes, and take care with children near the unfenced quays and river.