At least for the Western Australia end I would be very much factoring in the wind ... Perth and the south-west of WA is known for being windy. We even have infamous winds, the Fremantle Doctor
and the Albany Doctor [not so famous as to get is own wikipedia page
]  are two that come to mind.
Anyway for information on winds I suggest you refer to the BOM wind roses
and for temperature data see http://www.bom.gov.au/climate/data/
 I can recall many an evening when I lived in the wheatbelt sitting outside supping on a beer, to hear a roar coming across the paddocks to moments later have anything blown all over the place and grabbing a jumper. That was the Albany Doctor. A blessing on a hot evening, not such a blessing if you had to ride into it
You also need to consider that WA and the Nullabor are pretty flat so the wind tends to have free range across the paddocks and of course on the Nullabor a southerly is coming from Antarctic straight across the ocean into your face
My regular summer commute is south in the afternoon; 42 km of coastal riding into the Fremantle Doctor. Riding daily into a wind over summer which commonly blows at 40 km/h plus is not fun.
Personally I would be checking those roses