May is officially the beginning of the dry season. You'll still experience scattered showers throughout the month but they're not usually as intense as they are earlier in the year, particularly around Bali, and they don't last as long. You'll still want a light raincoat but you may or may not need it.
Temperatures are hot with plenty of sunshine and blue skies. Bali tends to linger in the 86°F to 90°F range while East Java is hotter, averaging 95°F to 97°F. Evenings stay warm, particularly in Bali where night temperatures rarely fall below 87°F to 90°F. Java is a bit cooler, averaging 68°F to 70°F at night. Overall, you'll want lots of sunscreen, hot weather clothes, and plenty of water.
Crowds and Costs
Tourist numbers definitely begin increasing in May but it's not like the middle of summer when the beaches are packed and you have to elbow for room at all of the restaurants and bars. Bali is the most heavily trafficked of the islands and definitely the one where you'll see the largest crowds. By contrast, places like the Moluccas or Raja Ampat are more remote and see far fewer tourists.
Cost-wise, May is a month when airlines and hotels begin switching over to high-season rates. You may still be able to snag some deals if you hunt around, but overall prices will be more expensive, especially compared to the wet season rates.
Where to Go
Just about everywhere in Indonesia is wonderful to visit in May. Bali, for instance, is warm and sunny with picturesque beaches and crystal blue water yet the crowds are smaller. You can enjoy popular destinations like Kuta, Ubud, Tanah Lot, and other spots that are normally crawling with people without all of the masses.
It's also an excellent month to climb any of the country's numerous mountains and volcanos, all of which will be dry and accessible. Among the many options include Mt. Bromo or Mt. Ijen in Java and Mt. Rinjani in Lombok.
Head to the islands of Nusa Tenggara, Flores, or Sumba where it will be dry and sunny with beautiful beaches and lots of outdoor opportunities. Diving off the coast of Lombok is stunning and it's also a wonderful time to visit Komodo National Park.
Sumatra is another great option. Temperatures will be around 80°F to 83°F and perfect for enjoying the beach or wandering through the temples and cultural sites.
Kalimantan experiences a light rainy season this time of year, that lasts from March to May, so it is one of the few islands that isn't ideal for a visit.
What to Do
In Bali, surf at Kuta beach, shop and dine in Sanur, or get your adrenaline fix in Tanjung Benoa riding a jetpack across the water. The southern part of the island is full of beach activities like snorkeling, scuba diving, sea kayaking, and other ocean sports. Farther north, visit Ubud where you can get close and personal with Balinese long-tailed monkeys at the famous Monkey Forest (Mandala Suci Wenara Wana) where they flock to tourists asking for bananas and other treats.
Try meditating or taking a class at the Yoga Barn, or make a trip to the silversmiths in a Celuk village just outside of town. From there, you can continue north to Bedugul to check out destinations like the Bali Treetop Adventure Park or the Bali Botanic Garden.
Head to Java and climb Mt. Bromo or Mt. Ijen. Or, if volcanos don't pique your interest, check out the sacred Borobudur Temple complex near Yogyakarta or the Candi Prambanan complex by Borobudur. If you have a hankering for some city life, swing through Surabaya, the second-largest city in the archipelago and digs into its food, shopping, and entertainment.
In Sumatra, visit the Mesjid Raya Al Mashun mosque in the northern city of Medan, or explore Istana Maimun, a royal palace that once belonged to the Sultanate of Deli. Or you can head to the south to Palembang, also known as the "Venice of the East." There, stop by the Great Mosque of Palembang or take a Musi River cruise.
Events in May
Waisak Day: Also known as "Buddha Day," this major Buddhist holiday is celebrated throughout Asia. The festival, which commemorates the birthday of Buddha, as well as his enlightenment, takes place on a full moon, typically in early to mid-May (although it occasionally falls in April). Thousands of monks gather in the town of Borobudur to chant in a ritual called "Pradaksina" that involves transporting holy water and flames.
Traveling to Indonesia in May? Check out this great itinerary
Temples and Trekking from East Java to Bali: This fantastic two-week itinerary incorporates all of the most scenic landscapes and sacred temples in both Bali and East Java. The trip includes a hike up three different active volcanos, a snorkeling trip through Mengangan Island's stunning coral reefs, and visits to both the Borobodur and Prambanan temples.