When is the best time to go to Bali? Always!
Daytime temperatures are pleasant, varying between 28–33⁰ C (68–93⁰ F) year-round. From December to March, the west monsoon can bring heavy showers and high humidity, but days are still often sunny with the rains starting in the late afternoon or evening and passing quickly. From June to September, the humidity is low and it can be quite cool in the evenings. At this time of the year there is hardly any rain in the lowland coastal areas.
Even when it is raining across most of Bali, you can often enjoy sunny, dry days on the Bukit Peninsula which receives far less rain than any other part of the island. On the other hand, in central Bali and in the mountains, you should not be surprised by cloudy skies and showers at any time of the year.
At higher elevations such as Bedugul or Kintamani, it gets distinctly chilly and you will need either a sweater or jacket after the sun sets.