The dry season from May to September is the best time to visit, with warm, mostly sunny days ideal for temples, Merapi and the beaches, though July and August are the busiest and priciest. The wet season from October to April brings heavy afternoon downpours, peaking in December and January, when open sites like Borobudur can be soggy. May and September offer a good balance of fine weather and thinner crowds.
Yogyakarta sits below Mount Merapi, one of the world's most active volcanoes, and in an earthquake-prone region. Eruptions and tremors are rare during a visit but do happen; follow official guidance and any exclusion zones, and only take Merapi jeep tours with established operators.
Traffic is dense and dominated by scooters that weave and rarely stop for pedestrians, and crossings are informal. Cross steadily with locals, take care on narrow pavements, and if you rent a scooter, wear a helmet and know that road standards are relaxed.
The temples and beaches are hot and exposed with little shade, and the equatorial sun is strong. Carry water, wear a hat and sunscreen, and time Borobudur, Prambanan and the coast for the cooler early morning or late afternoon.