The dry season (May to October) is the best time to visit Borobudur. Clear mornings increase the chance of a spectacular sunrise from the top terraces, with the volcanic peaks of Merapi and Merbabu visible above the mist on the Kedu Plain. July and August are peak tourist season and the site can be crowded; early May and September–October offer good weather with fewer visitors.
The wet season (November to April) brings daily rain, often in the afternoon, and reduced visibility. Sunrise visits are possible but less reliably spectacular. The Vesak festival (the Buddhist celebration of the Buddha's birth, enlightenment, and death) falls on the full moon in May or June and draws large pilgrimages — the procession from Mendut Temple to Borobudur is a genuinely moving spectacle, but accommodation books out far in advance.
For sunrise visits in any season, arrive at the temple by 5:30am. The number of visitors allowed on the upper terraces at dawn is limited; buy tickets in advance online, particularly in high season.