Bali, Indonesia is located in the Southeast of Asia. Neighboring countries are the Philippines, Malaysa, Thailand, etc. Similarly, they have more or less the same weather. That is, Tropical Moonsoon Climate. Moonsoon usually refers to the wind, but throughout the year even with rain moonsoon, it may still happen that during the day it will be sunny.
From the months of April to September, there is dry and rainy days but usually only infrequent and with less intensity. From October to March, it is the rainy season, with December as usually the most rainy. But since this is tropical weather, it can rain anytime. Southeast Asian weather is usually very unpredictable and dynamic and rapidly changes from time to time.
“The daytime temperature averages between 80º F (27ºC) to 90º F (32ºC) in the southern lowlands. In Bali however, it is quite humid at about 75% so often times it feels much hotter. The mountains tend to be significantly cooler at around 70º F (21ºC) to 80º F (27ºC)” (http://www.tripadvisor.com/Travel-g294226-s208/Bali:Indonesia:Weather.And.When.To.Go.html).
In the coastlines or near the beaches, the heat of the sun is cooled by the cool sea breeze and moving inland towards Bali, it gets cooler since the altitude also goes up that works by cooling as you go up through the mountains. These times, a jacket, sweater or hoody is highly recommended.
The best time of the year to visit Bali is in the months of May through August where the climate is cool and if it does rain, it’s only light. But this also depends on the kind of traveler you are. If you are adventurous and yearn for the gusty winds, during the dry season, the western side of the Bali peninsula creates waves that are world-renowned and are visited by avid surfers from all over the globe.
Lastly, for all your inquiries, concerns and up-to-date information regarding the weather in Bali, Indonesia, you can check this link as it gives real-time updates on Bali weather.