The Official Mt. Fuji Climbing Season:

The offical general Mt. Fuji climbing season for each route are as below:
 
*The opening and closing dates vary from trail to trail.
*The opening dates of the trails are announced, on the first day of July or later depending on their condition.
 
 
Yoshida Route is generally open from July 1st to September 14th:
Fujinomiya Route is generally open from July 10th to September 10th:
Subashiri Route is generally open from July 10th to September 10th:
Gotenba Route is generally open July 10th to September 10th:
 

Changes in climate have extended the official climbing season from previous seasons.
After the dates above all public toilets and safety facilities close.
Some mountain huts remain open after the official climbing season is finished.
The dates the mountain huts remain open vary from year to year and depend on the hut. 
The shops and restaurants at the Fuji-Subaru Line 5th station (The Largest 5th station on Mt. Fuji) remain open as long as access via the Subaru line toll road remains open. Sometimes road access is closed in the winter due to snow conditions.

Read more: The Mt. Fuji Official Climbing Season: