Karimunjawa in September

April through October offers your best shot at perfect weather. The dry season means calm seas, clear skies, and excellent visibility for snorkeling and diving. July and August are peak months – expect higher prices and more crowds, though 'crowds' here means maybe 50 other tourists instead of 20. May and September hit the sweet spot: great weather with fewer visitors and better accommodation deals. The water temperature stays around 28°C year-round, so you can snorkel comfortably in just board shorts. Avoid November through March if possible. The rainy season brings rough seas that can cancel boat trips and strand you on the main island. Some accommodations close entirely during these months, and the ones that stay open often deal with flooding. But here's something most guides won't tell you: even during dry season, afternoon thunderstorms happen. They're usually brief but intense. Always carry a waterproof bag for your electronics and don't plan crucial activities for late afternoon. Weekends see an influx of domestic tourists from Java, especially during Indonesian holidays. If you want maximum solitude, aim for weekdays during shoulder season.