What is the humidity level of Vegas in September? I know it cools off in Oct/Nov timeframe.
It does cool off, but you're still going to get those really humid days from time to time. I mean, it is Vegas, so you're not going to get this crazy cool weather. It'll mostly be warm, but the humidity might calm down. But don't take my word for it.
I feel like Vegas is pretty humid year round, but I am not there all the time, so can't say 100% for sure. All I know, is that each time I went to Vegas, it's often been pretty hot for the most part. There were days where it reached 60 some degrees, and that's weather I can do often, but when it hits 80 and above, I can't do it.
I haven't been there year round, so I can't verify it all, but I was there around August of 2017, and it was pretty hot. Not too humid though. But I think it eventually cools down a bit more in September and October.