Valaam is only accessible in summer, roughly May to October, when the lake is ice-free and boats can run. July and August bring the best weather — long days, warm enough to swim from the rocks, and the full flowering of the monastic gardens. June has the white nights that make the island feel genuinely otherworldly. September is quieter and the forests turn golden, but the hydrofoil schedule thins out. In winter the lake freezes solid and access is effectively impossible; the monks remain year-round.