But our summers break 110F. I have a feeling that is hotter than in Brisbane.
What sort of humidity do you get in Arizona? I'm guessing it's probably close to the humidity in Vegas - that is, not present. We may only hit the mid-20'sC here in Auckland, but the constant 80%+ humidity makes it feel much, much higher.
Example: It is currently 0430 here, 19C, but the 93% humidity is pushing that up to 21C. And that's with some light wind.
This is why I sleep with a fan constantly blowing on my face.