It’s hot, humid and sunny most of the year, typically over 30 degrees celcius. Bring cool, light, summer clothing. If heat is challenging for you when sleeping, check that the accommodation you are considering has air conditioning. It does cool down in the evening a touch during the June-August season. If you choose to venture north or to the volcano, it gets chilly. So bring one light jacket or sweater.
There are essentially two seasons in Bali, wet and dry. The seasons vary but generally, the wet season runs from around November to April before things start to dry out again. The driest time of the year is probably June to September. This is also cooler at this time of the year and it’s the peak time for tourist visits. During the wet season expect brief but torrential downpours. Rain ponchos and umbrellas are cheaply and easily purchased