Røst is above the Arctic Circle, which shapes everything about when to visit.
Summer (June to August) is the best time for birdwatching — the seabird colonies are active and boat trips run to the outer islands. The midnight sun means daylight around the clock from late May to mid-July. Temperatures are mild by Arctic standards, typically 10–16°C, but the wind rarely lets up.
Winter (January to April) is the season for stockfish, when the drying racks are full and the island is at its most working. The Northern Lights can be seen on clear nights. Temperatures hover around freezing; the Gulf Stream prevents it from getting as cold as you might expect this far north.
Spring and autumn are quieter. Storms can be severe in October and November.
Whatever time of year you come, pack layers, waterproofs, and windproof gear. The wind is constant and can be brutal.