Leadville's altitude — 10,152 feet — shapes everything. Summers are cool and dry, with afternoon thunderstorms common from July through September. The hiking season runs from late June to early October, when the fourteener trails are clear of snow. The Leadville 100 ultramarathon takes place in mid-August and fills the town's limited accommodation well in advance.
Winter brings reliable snow and the ski season at Ski Cooper. The town is quiet from October to December and again in April and May, when the ski season has ended but the hiking season has not begun. Spring can bring heavy snow through May. Acclimate slowly if you are arriving from low elevations — altitude sickness is a real issue at Leadville's elevation.