So here are the facts. Bali is located 6 degrees from the equator, so the temperature variance throughout the year is minimal. The daytime temperature range is between 29C (84F) to 32C(90F). Humidity ranges between 55-75% which often makes it seem warmer than the temperature would indicate.
While it does get cooler in the evening, you would normally be comfortable with bare arms. Bring one pashmina/cardigan/long sleeved shirt and you will be fine!
You may be interested to know that on average the warmest month is March, the “coolest” month September and the rainiest month is January. Sunrise is always around 6am and sunset about 6pm.
Sunscreen and hats are highly recommended.