Eight degrees south of the Equator, Bali has a tropical climate. There are basically two seasons: wet and dry.
The rainy season runs from mid-October through mid-April. The dry season runs from late April through early October.
The heaviest rains can be expected between December and February. There can be cool breezes between June and August.
Rarely mentioned in travel guides is something called 'Mango Season', which runs about one month. This is when the mangoes ripen, which causes a proliferation of flies – not pleasant given Bali's outdoor lifestyle.
Needless to say, hotels and resorts do their best to mitigate against the problem.
I stumbled across mango season on the final days of one of my trips. We were unable to enjoy breakfast outdoors. We couldn't even lie outside on the day beds. We were confined to the inside of our villa – or the swimming pool.
Unfortunately, there's no way of knowing for sure which month Mango Season will fall because it varies from year to year. But it's usually falls in either September, October, or November.
Peak and Low Seasons
The peak seasons are Christmas and Easter as well as the months of July and August. Expect to pay a premium at hotels and resorts.
The low seasons are January through April and October and November. Expect fewer people and lower prices.
Bali Arts Festival - a celebration of Balinese and Indonesian culture with daily performances, exhibitions, and other activities. Held throughout the island mid June through mid July.
Bali Live International Jazz Festival - Four days of jazz at select venues throughout the island.
Bali Kite Festival - A colourful religious festival held at Sanur Beach in July when the winds tend to be strong, with villagers appealing for abundant crops from the gods with giant kites.
Ubud Writers and Readers Festival - Held for a few days in October, drawing artists, writers, and literature buffs from around the world. Events include poetry readings, cultural performances, and book launches.
Nusa Dua Festival - a week of cultural events and performances held each October with a new theme each year.