If you schedule your event during peak event season (June to October) you may be competing with lots of other events. June to October is the cooler and dryer part of the tropical year in Cairns, which is why these months are so popular. If you are holding your event indoors, the weather becomes less of a problem and you can consider holding the event in the low season (Nov – May).
The Cairns region has a fabulous tropical climate ideal for outdoor enjoyment. Cairns enjoys a winter period of pleasant temperatures and low rainfall (“dry” season April to October) and a summer period of warm temperatures with increased rainfall ("wet" season November to March).
Some events are traditionally held at the same time each year, so you might want to reconsider holding your event on one of these dates. For example Australia Day or the Easter weekend would be a poor choice of dates, as would be ANZAC Day or the AFL and NRL Grand Final dates.
Council’s What’s On Calendar is not only a good place to advertise your event for free, it is also a good reference tool. Check this calendar to see what other events are on around the same time as you are thinking of hosting your event.