Semisopochnoi Island
Island Volcanic island in Aleutians, Alaska
A remote Aleutian island, Semisopochnoi is volcanic, uninhabited and marked by rugged craters and seabird colonies. Scientists and experienced visitors come for volcanology, birdlife and boat‑accessible, extreme wilderness.
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.
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.
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.
January
January is the coldest month with highs of -1°C and lows of -4°C. Moderate rainfall (67 mm) and windy conditions.
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February
February is freezing with highs of -1°C and lows of -4°C. Moderate rainfall (58 mm) and windy conditions.
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March
March is freezing with highs of 0°C and lows of -3°C. Moderate rainfall (67 mm) and breezy conditions.
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April
April is cold with highs of 2°C and lows of -1°C. Moderate rainfall (70 mm) and breezy conditions.
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May
May is cold with highs of 4°C and lows of 1°C. Moderate rainfall (63 mm) and breezy conditions.
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June
June is cold with highs of 7°C and lows of 4°C. Moderate rainfall (57 mm) and breezy conditions.
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July
July is cold with highs of 11°C and lows of 6°C. Moderate rainfall (76 mm) and breezy conditions.
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August
August is cold with highs of 11°C and lows of 7°C. Significant rainfall (117 mm) and breezy conditions.
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September
September is cold with highs of 9°C and lows of 5°C. Significant rainfall (107 mm) and breezy conditions.
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October
October is cold with highs of 6°C and lows of 2°C. The wettest month with heavy rain (141 mm) and breezy conditions.
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November
November is cold with highs of 2°C and lows of -1°C. Significant rainfall (114 mm) and breezy conditions.
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December
December is freezing with highs of 0°C and lows of -3°C. Regular rainfall (82 mm) and windy conditions.
