I drove adelaide to townsville via Darwin 2 or so years ago in summer and met two Germans riding it. Was over 40 degrees most days but they were planning to ride all the way from North to South.
Except for a few gradual up and down bits on the way to yulara it’s very flat and not too windy so you should be able to do good distance each day There’ll be water on the Stuart highway and the road between it and yulara every 100kms or so. Be prepared to carry 10L I guess? The Germans had 25 each… Crazy Germans.
For most of Australia, I’m certainly one to carry quite a bit more water than I think I’ll need. I’d recommend a decent safety gap, but you probably won’t use it.
You’ll be going quicker than us though, and you should be able to get water from this hut I mentioned:
5.2L isn’t a lot of room for error out there ATMO, but I’m overly anxious about these things, and I don’t mind carrying a bit of extra weight for it. Remember that cooking and coffee uses a bit.