i lived in vegas for a year and the humidity was 10% to 15% usually, dry is good especially near the end of your flower like the last few weeks, it will push your tricrome development so i hear.
30% is good for vegas and just fine for flowering keep your humidity up to at least 50 during the first 2 months of growth, and low in flowering, just keep your area clean and use good organic nutes and keep them critters out