Climate
June is winter in the southern hemisphere. The Gold Coast tends to have a mild winter though. The average temperature at this time of year is about 20ºC.
There is usually a nip in the air at night, so it is advisable to bring warm clothes. It's a different story during the day. You won't need to rug up much during the day - if you need to rug up at all.
Many of the locals will shy away from swimming at this time of the year. The tourists must be more hardy though, because it is not unusual to see them going for a winter dip.