Takayama is at its busiest during the two halves of the Takayama Festival — 14–15 April (Sannō Matsuri) and 9–10 October (Hachiman Matsuri). Both are among the most spectacular festivals in Japan and accommodation books up months ahead. If your timing allows it, one of these is a genuine bucket-list experience; if not, avoid those dates for the same reason.
Autumn (mid-October to mid-November) is the visual peak, with the surrounding mountains in colour. Winter (December to March) is heavily snowy and quietly beautiful — many shops shorten their hours but it is the best time to combine Takayama with a visit to the snow-locked Shokawa Valley. Summer (June to September) is mild and pleasant; the cherry blossom usually arrives in mid-April, around the spring festival.