Fuji's peak is almost always below freezing and the annual average temperature is -7.1^oC. Even on days when the temperature at level ground is 30^oC, if you climb to Gogoume it drops to 16^oC and is only 7^oC at the peak. There is a 22^oC average difference throughout the year between the level ground of Mishima and Mt.

The temperature at the summit of Mount Fuji is extreme and significantly colder than the ground level. Even during the official climbing season (July to early September), the average temperature at the peak typically ranges from 5°C to 8°C (41°F to 46°F) during the day, and it frequently drops below freezing at night or in the early morning. Outside of the summer months, conditions are lethal; from November to April, temperatures at the summit often plummet to -20°C or even -30°C (-4°F to -22°F). A helpful rule of thumb is that for every 100 meters of elevation gain, the temperature drops by about 0.6°C; thus, when it is a sweltering 30°C in Tokyo, it could easily be near 0°C at the top. Additionally, the wind chill factor is severe; the average wind speed at the summit is often over 15 meters per second, which can make the perceived temperature feel 10 to 15 degrees colder than the thermometer suggests. Proper high-altitude gear and layering are essential for any climber to prevent hypothermia, even in the height of summer.