The dry season is not automatically the right answer. A month-by-month look at what you actually gain and lose.
Java has two seasons: wet, roughly November to March, and dry, roughly April to October. Almost every itinerary you will read recommends the dry season, and for volcano hikes that advice is sound.
But the shoulder months are underrated. April and October give you most of the clear mornings with a fraction of the visitors, and the landscape is still green rather than dusty.
The wet season is not off the table either. Rain on Java tends to arrive in the afternoon and leave within two hours. Temples in the morning, a long lunch, and a green plateau to yourself is not a bad trade.
The exceptions are firm: Karimunjawa crossings get genuinely rough between December and February, and the Ijen night hike is unpleasant and sometimes closed in heavy rain.
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