Semisopochnoi IslandSemisopochnoi Island at a Glance
About Semisopochnoi Island
Semisopochnoi Island is an uninhabited volcanic island in the Aleutian Islands of Alaska and is part of the broader Alaska Maritime National Wildlife Refuge.
The island is notable for volcanic landscapes including a central caldera and volcanic cones, and for its seabird colonies and remote tundra environment; there are no visitor facilities and access is rare and challenging.
Volcanism has shaped the island’s terrain; it is monitored by the United States Geological Survey because of ongoing volcanic activity. There is no permanent civilian population and the island has been used intermittently for scientific and military purposes in the past.
Located in the Aleutian chain near the International Date Line, the island lies in the northern Pacific under the jurisdiction of the U.S. state of Alaska.
- Access: The island is remote and uninhabited; access is by sea or air only and is subject to strict weather and logistical constraints.
- Conservation status: Part of the Alaska Maritime National Wildlife Refuge, the island is monitored for volcanic activity and supports seabird colonies and marine wildlife.
Best Time to Visit Semisopochnoi Island
The very short Arctic summer is the only practical time for visits; careful planning and experienced operators are essential.
Weather & Climate near Semisopochnoi Island
Semisopochnoi Island's climate is classified as Tundra - Tundra climate with cold summers (peaking in August) and freezing winters (coldest in January). Temperatures range from -4°C to 11°C. Abundant rainfall (1019 mm/year), wettest in October.
| Month | Comfort | Temp | Feels | Rain | Sky | Humidity | Wind | UV | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | - | -4° - -1° | -11° | 67 mm | - | - | 10.5 m/s | - | - |
| February | - | -4° - -1° | -10° | 58 mm | - | - | 10.0 m/s | - | - |
| March | - | -3° - 0° | -9° | 67 mm | - | - | 9.8 m/s | - | - |
| April | - | -1° - 2° | -6° | 70 mm | - | - | 8.6 m/s | - | - |
| May | - | 1° - 4° | -3° | 63 mm | - | - | 7.8 m/s | - | - |
| June | - | 4° - 7° | 1° | 57 mm | - | - | 7.0 m/s | - | - |
| July | - | 6° - 11° | 5° | 76 mm | - | - | 6.6 m/s | - | - |
| August | - | 7° - 11° | 6° | 117 mm | - | - | 6.9 m/s | - | - |
| September | - | 5° - 9° | 3° | 107 mm | - | - | 7.7 m/s | - | - |
| October | - | 3° - 6° | -1° | 141 mm | - | - | 8.6 m/s | - | - |
| November | - | -1° - 2° | -6° | 114 mm | - | - | 9.2 m/s | - | - |
| December | - | -3° - 0° | -9° | 82 mm | - | - | 10.0 m/s | - | - |
How to Get to Semisopochnoi Island
Access is by charter or authorized vessel from Alaskan ports (e.g., Adak); landing is weather-dependent and often arranged only for scientific or refuge work.
Tips for Visiting Semisopochnoi Island
- Approach with experienced Arctic or Aleutian guides - the island's weather is unpredictable and landing sites can be difficult.
- Respect protected areas - parts of the island are designated wilderness and bird nesting sites are vulnerable.
- Be prepared for no facilities: bring all supplies and emergency communication gear.