Yes, it can. And the desert has special heat problems. I gather Reloader 15 is being replaced with IMR 4064 in a newer version (Mk316?) of M118LR for sniping because of high temperature pressure issues in desert conditions. IMR 4064 and Varget both tend to gain less velocity with charge weight increments than some other powders, making them less sensitive to other pressure influences. However, I've also seen that Varget seems to do this betting in .308 than in .223. Take a look at this article
for some more general information on temperature influence. It turns out barrel temperature seems to have more effect than ambient powder temperature, so if your load works well fired at a fairly brisk pace, you should be OK with it. Especially since the pressure is likely modest in most AR chambers.