In specific, the average high temperature reaches 18? (64.4?) merely, while the average low temperature is as low as 12? (53.6?). The rainfall and humidity also decrease a little in September around Mt. Fuji compared with previous months.

In September, the weather at Mount Fuji transitions from summer humidity to a cooler, crisper autumn climate, though it remains quite unpredictable. At the foothills (5th Station area), temperatures are generally pleasant, with average highs of 18°C–24°C (64°F–75°F) and lows of 12°C–15°C (54°F–59°F). However, September is also one of the rainiest months due to the tail end of the typhoon season; the area receives an average of 143mm of rainfall across roughly 11 rainy days. If you are climbing toward the summit (note: the official climbing season usually ends in early September), temperatures can drop well below freezing, requiring heavy thermal gear. For general visitors, the humidity is lower than in August, offering a better chance of seeing the peak through the clouds, though thick afternoon fog is still common. Visitors should pack layers, including a waterproof jacket, to handle the frequent rain showers and the significant temperature drop as you ascend the mountainside.