Hi Kiting Sarah
Rain usually and I mean usually doesn't really start until Jan, however, we have had a wet year by averages already.
For the wind it is very unlikely to be kiteable (sub 10 knots) and you have the stingers to contend with which can be life threatening. We are unfortunately coming to the end of our season (that never really happened this year

)
Plus the heat and humdity, Cairns is not really a great spot to be in December.
Cheers