I went in August which is better in the Jelly Fish department (or so I was told).
Yup. Every time I went was in their winter.
No cyclones
no Jelly fish issue.
only downside is that it is colder, but who cares? I'm on a boat on the GBR diving one of the best places out there
If it snow'd I'd still be in the water (and I did dive while it was snowing before - in a wet suit)