Mt. Fuji Weather Station Day

What Is Mt. Fuji Weather Station Day?

Every August 30th is "Mt. Fuji Weather Station Day" (富士山測候所記念日, Fujisan Sokujo Kinenbi) in Japan. On August 30, 1895, meteorologist Nonaka Itaru (野中至) established a private weather observatory at the summit of Mt. Fuji — at 3,776 meters above sea level, the highest point in Japan — becoming the first person to maintain a permanent weather observation station on the mountain's peak. Nonaka's achievement — surviving a brutal winter alone at the summit with his equipment — demonstrated that systematic meteorological observation from Japan's highest point was possible and scientifically valuable.

Nonaka Itaru's Extraordinary Winter

Nonaka Itaru was a meteorologist who believed that weather observations from the summit of Mt. Fuji — far above most weather phenomena — would provide crucial data for understanding Japan's atmospheric conditions. In 1895, with his wife Chiyoko by his side (who joined him partway through the winter), he spent the winter months at the summit in a tiny stone hut, recording weather data in conditions that nearly killed him. He survived temperatures below -30°C, hurricane-force winds, and complete isolation. His systematic observations provided data of scientific value and proved the concept of high-altitude meteorological observation on Fuji.

The Mt. Fuji Weather Station: 1932–2004

Inspired by Nonaka's work, Japan's Central Meteorological Observatory established a permanent, government-operated weather station at Mt. Fuji's summit in 1932. The station operated continuously for 72 years, providing invaluable data on upper atmospheric conditions, typhoon tracking, and long-range weather patterns. The summit observatory became a landmark of Japanese meteorological science — staffed by meteorologists who rotated through demanding tours of duty at Japan's highest, harshest point. The station closed as a continuously staffed facility in 2004, replaced by automated instruments, though it continues to be used for research during summer months.

Mt. Fuji's Scientific Legacy

Mt. Fuji's altitude and isolation from surface-level pollution have made its summit a site of valuable atmospheric and environmental research beyond meteorology. Studies of ozone concentrations, aerosol chemistry, and long-range transport of atmospheric pollutants from continental Asia have all been conducted from the Fuji summit. The mountain's scientific significance adds another dimension to its status as Japan's most beloved and most climbed peak.

Fun Facts

• Summit conditions: The average temperature at Mt. Fuji's summit is -6.5°C annually; in winter, temperatures regularly fall below -30°C with wind chills far lower. The meteorologists who staffed the summit station endured some of the harshest working conditions of any scientific post in Japan.
• Climbing season: Mt. Fuji's official climbing season runs from early July to early September, when trails are open and mountain huts operate. Approximately 300,000 people climb Fuji each year, making it one of the world's most-climbed mountains.