You’re Correct!

Answer: (a) April

Mt. Fuji covered with snow

Snow on Mount Fuji

The only time when Mount Fuji’s summit isn’t covered in snow is during a short time during the summer months. Therefore, the summer months mark the official climbing season during which the mountain is quite crowded with visitors. As this is the only time when the rest houses (known as huts) and other businesses on the mountain are open for business, it is the most convenient?as well as the safest?time to tackle the mountain. During the off-season, while it is possible to climb Mount Fuji, bathrooms, food and water as well as places to rest are mostly unavailable. For this reason, the number of climbers decreases dramatically. Usually, the snows begin during late September. And accumulating over the winter, mid-April usually experiences the highest snow coverage. After this time, the snows gradually melt with the rains during the rainy season and the strong sunshine of summer.

Since the Mount Fuji Weather Station began its meteorological observations in 1936, Fuji’s earliest ever “first autumn snowfall” was recorded on July 31, 1963 and the latest first autumn snowfall on October 16, 1943. This compares to the September 12 average. The “first autumn snowfall” is defined as the first time it snows on the summit after the summer temperature peak.

Temperatures and Wind on the Mountain

Apart from summer, the monthly average temperature at the peak is mainly below zero with a monthly average of -6.4 degrees Celsius. Even when temperatures are 30 degrees down at the bottom, it will only be 16 degrees at the Fifth Station and a frigid 7 degrees at the peak. The annual average difference in temperature between the peak and the town below is 22 degrees. In addition to very cold temperatures, the peak also experiences extremely strong winds; receiving westerlies or northwesterlies year round. With yearly average wind speeds of 12 meters per second, these winds make the temperatures feel much, much colder. The winds also create dangerous conditions for climbers, so only the most experienced climbers should ever attempt climbing the mountain during the off-season.

The Peak’s Radar Station

With the hope of being able to detect meteorological changes that would help forecast the approach of dangerous typhoons, putting a weather station on the top of Japan’s highest mountain was something discussed as early as 100 years ago. Although meteorological observations had been done from the summit of the mountain since 1880s, a weather station was set up to begin implementing year-round meteorological observations in 1932. Proving to be effective, in 1936, the weather house was moved to the Kengamine Peak where it became a permanent installation. At the time, it was the world’s highest located permanent weather station. Then, in September 1964, radar equipment was set up, and it is this radar dome that has become synonymous with the highest peak of the mountain.

The now-closed Mount Fuji Radar Station was designated as an IEEE Milestone.

The radar installation was a triumph in engineering of the times. Construction on the peak was only possible during the short summer months, and even then it proved extremely difficult due to sudden updrafts from the craters. Operation of the radar started in full swing in March 1965. However, with the advent of satellite technology, by the 1990’s the equipment had become obsolete, quietly closing down observation in 1999 after 35 years.

To acknowledge the station’s excellence in technological achievement, in 2000, the now-closed Mount Fuji Radar Station was designated as an IEEE Milestone by the Institute of Electrical and Electronics Engineers, a non-profit organization that is the world's leading professional association for the advancement of technology. The radar itself is now housed in the Mount Fuji Radar Dome Museum, located in the city of Fujiyoshida.