Rain is coming back. After September, which is still dry season, October feels more like rainy season at times, although it could be this or that. On an average there are 15 days with rain fall in October, but with little rain.
It’s still a great month to come here. And even if it rains, Bali still offers many great activities off the beach. Definitely a good month to get cheap hotel rooms and villas, as it is definitely low season. Some international festivals draw in a crowds in certain areas at times, but in general you will experience a quiet Bali.