Mount Kusatsu-Shirane
Volcano Active volcanic complex with sulfur fumaroles and lakes
A volcanic complex near Kusatsu Onsen, noted for crater lakes and fumarolic activity. Day visitors combine crater walks with nearby hot-spring baths and ski slopes, but advisories about volcanic activity sometimes restrict access.
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Mount Kusatsu-Shirane is a volcanic complex in Gunma Prefecture, Japan, with summit elevations around 2,160 metres and multiple crater features. It is known for both its volcanic activity and nearby hot-spring (onsen) resorts.
Hiking trails and ropeway access in the region lead to viewpoints around the summit area and to the crater lake Yugama, a striking acidic lake noted for its vivid green colour. The wider area also supports year-round tourism tied to onsen resorts and winter sports at nearby facilities.
The complex has produced phreatic eruptions in historical times; its hydrothermal system has created crater lakes and fumarolic activity. Local authorities periodically monitor the volcano for sudden steam-driven eruptions and issue advisories as needed.
Located in central Honshu within Gunma Prefecture, the volcanic complex sits inland from the Sea of Japan and is accessible from regional roads and resort towns in the Kusatsu area.
- Elevation and summit features: Summit elevations for the complex are around 2,160 metres and include multiple peaks and crater features.
- Volcanic activity and hot springs: Known for active hydrothermal features and hot-spring activity in the surrounding Kusatsu onsen area, with monitoring for volcanic hazard.
What to See #
- Yugama crater lake: An acidic crater lake with vivid green water located near the summit, formed in a crater created by phreatic activity and often visible from nearby trails.
How to Get to Mount Kusatsu-Shirane #
Kusatsu Onsen is accessible by bus from Naganohara-Kusatsuguchi Station (on the JR Agatsuma Line) or by highway bus from Tokyo (approximately 3-4 hours). From Kusatsu town, local roads lead to trailheads and viewpoints around the mountain complex.
Tips for Visiting Mount Kusatsu-Shirane #
- Winter crater area can be dangerous-obey local advisories and ride closures; sulphur fumes and steam vents have been hazardous in recent years.
- In summer, drive to the Kusatsu area early to avoid road congestion; several onsens and ryokans make a good base for visiting the mountain's surroundings.
- Respect signs and barriers: parts of the mountain have thermal activity and fenced-off hazard zones.
Best Time to Visit Mount Kusatsu-Shirane #
Spring through autumn for safe access and clearer trails; check local advisories for volcanic activity and crater access.
Weather & Climate near Mount Kusatsu-Shirane #
Mount Kusatsu-Shirane's climate is classified as Warm-Summer Continental - Warm-Summer Continental climate with mild summers (peaking in August) and freezing winters (coldest in January). Temperatures range from -13°C to 20°C. Abundant rainfall (1960 mm/year), wettest in August.
January
January is the coldest month with highs of -4°C and lows of -13°C. Moderate rainfall (62 mm), partly cloudy skies, and breezy conditions.
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February
February is freezing with highs of -4°C and lows of -13°C. Moderate rainfall (72 mm), partly cloudy skies, and breezy conditions.
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March
March is freezing with highs of -1°C and lows of -10°C. Significant rainfall (102 mm) and partly cloudy skies.
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April
April is cold with highs of 6°C and lows of -4°C. Significant rainfall (146 mm), partly cloudy skies, and breezy conditions.
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May
May is cold with highs of 12°C and lows of 1°C. Significant rainfall (166 mm) and partly cloudy skies.
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June
June is cool with highs of 16°C and lows of 6°C. Heavy rain (240 mm) and mostly overcast skies.
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July
July is cool with highs of 19°C and lows of 11°C. Heavy rain (263 mm) and mostly overcast skies.
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August
August is cool with highs of 20°C and lows of 12°C. The wettest month with heavy rain (312 mm) and mostly overcast skies.
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September
September is cool with highs of 16°C and lows of 8°C. Heavy rain (280 mm) and mostly overcast skies.
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October
October is cold with highs of 11°C and lows of 1°C. Significant rainfall (159 mm) and partly cloudy skies.
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November
November is cold with highs of 6°C and lows of -4°C. Significant rainfall (101 mm) and partly cloudy skies.
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December
December is freezing with highs of 0°C and lows of -10°C. Moderate rainfall (57 mm) and partly cloudy skies.
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