April to September is the best time to visit Bali. Being a tropical country, it experiences relatively dry weather during these months. Even among these, the best months are the months of July, August and December. Travellers from all over the world come during this time and in terms of nightlife, the crowd, and the activities offered - it is indeed the best time to visit. Even for activities such as scuba diving, snorkelling, and deep sea diving - the weather is ideal as the visibility and sea condition is relatively stable.
January to April, qualify as the shoulder season for Bali as the weather is less than ideal to travel but the prices for accommodation, transport, food and beverages are slashed nearly in half.
October to April qualify as the off season in Bali as the seas are usually rough and monsoon takes hold of this Indonesian island. This leaves very little room for beach activities and watersports.