Seems reasonable. You are leaving late enough to not have as many issues with snow in the northern reaches. My guess is the largest weather issue to watch for weather will be further south in New Mexico where there can be longer stretches without water an temperatures warm but not extreme. For example, Deming is a little east of your route but a reasonable representation of the last part of desert getting to Antelope Wells. Average high temperatures a little over 30C - https://weatherspark.com/y/145595/Av...tes-Year-Round in August. Late summer has lower averages than June, in part because this is "monsoon" season Nothing extreme (this is still desert) but a larger chance of afternoon showers cooling things down and hence a lower high on average. Compared to OZ, still reasonable... warmer than Adelaide but not as hot as Coober Pedy...
https://weatherspark.com/compare/y/1...edy-and-Deming