Bali has two types of season wet and dry.
You can visit Bali all year round and have an amazing time and surf great waves.
The dry season is from May to October/November and then the west and south coast are pumping with waves. The weather is usually very sunny and hot during the days and the nights are usually a bit colder and the humidity goes down.
The wet season is more or less from October to April/May and then the humidity goes up and it gets warmer. It usually only rains shorter showers during the evenings and the sun normally shines during the day. During these months the waves on the east coast are great.
Read our blog post HERE about things to do in Bali during wet season.