4. Temperatures are ideal in the regions where it's spreading
https://www.scientificamerican.com/article/why-do-we-get-the...
In a binary sense, yes it “is spreading”. Even an R0 of 0.1 is “spreading”. But there is hardly enough data to say it is spreading widely in Australia.
The virus spread in summer/tropical vs winter/non-tropical regions is orders of magnitude different. But this is also not definitively causal. Just extremely highly correlated.