For seeing Fuji clearly, the best time is a clear morning from late autumn through winter (roughly Nov–Feb), when the air is driest and the snow-capped summit shows. To climb it, you must go in the official season, July to early September. Either way, mornings beat afternoons — clouds build over the summit as the day warms.
Fuji hides often. Summer is the worst for views — humid and hazy — even though it's the only climbing season. If a clear view is your goal, watch the forecast and webcams and be ready to go on the right morning rather than locking a fixed date.
Clear mornings from late autumn through winter (about November–February). The air is driest then and the snow-capped summit is most reliably visible.
Only during the official season, July to early September, when the trails and mountain huts are open. Outside that window the climb is closed and dangerous.