Here is the link to the Peak Crossing weather. Scroll down to the blue bar, and click on the Long Range Rainfall tab.
https://www.weatherzone.com.au/qld/southeast-coast/peak-crossingIf you pack for a wide range of weather conditions you will have a comfortable time. Pack clothes that will take you from a hot afternoon to a cold evening. Clothes you can layer are the best choice. Whether you are staying onsite or not, see the suggested list
"What to bring"Amaroo’s environment and climate can be demanding. The grounds are designed for walking and there is limited transport onsite. We suggest that you wear comfortable walking shoes, bring a hat, bottled water and a jacket to all event activities. A UV 50+ umbrella provides cool shade when walking to and from the Amphitheatre in the heat of the day. When the sun sets, it can become cold so make sure you pack a warm waterproof jacket.