Chur is pleasant in all seasons, but the logic of when to visit depends on what you want to do. In summer (June to September), the mountain hiking is at its best, the Rhine valley is green, and the city has a lively outdoor cafe culture. The ski resorts of Arosa and Lenzerheide are operational from December through April; the Glacier and Bernina Express trains run year-round, though winter adds the drama of snow-covered passes to the journeys.
Spring and autumn are the quietest times, when the crowds thin out and the light in the old town is at its most interesting — low-angled and golden in October, bright and green in April and May. The Chur carnival (Fasnacht) in February is a boisterous local tradition if you happen to be in the region.
The city's altitude (580 metres) keeps temperatures moderate in summer: comfortable rather than hot, with cooler evenings than the Swiss Mittelland. In winter, expect temperatures around zero and occasional snow in the city itself, though snowfall in the valley is less reliable than at the higher resorts.