Indonesia's equatorial climate means the dry-versus-wet season split matters more than temperature, which stays warm nearly year-round. Dry season, roughly April to October, is the most reliable window.
Dry season (April–October) brings the most reliable weather for Bromo treks, Komodo boat trips and Raja Ampat diving — also the busiest and most expensive season, especially July and August.
Shoulder months, April and October specifically, offer a good balance of dry-season weather and thinner crowds.
Wet season (November–March) still works well for Bali and Java, with short, heavy daily downpours rather than constant rain, though rougher seas can disrupt boat-dependent trips to Komodo or Raja Ampat.
Ramadan, which shifts each year, sees shorter daytime hours at some restaurants in Muslim-majority Java, though Bali and most tourist infrastructure carry on largely as normal.