High season is during the months of July and August, during Easter Holidays, and Christmas / New Year (December till 1st week of January). This is the time Bali is the busiest. However, for many reasons, best time to come to Bali is April, May, June and September, just before and just after high season.
The driest month of the year is August, and the wettest is January. Hence, the most popular months to come to Bali are April, June, July, August, and December. The least popular months are September, October, November, January, and February.