In my personal subjective experience, "dryness" is more of a comfort factor when the air temperature is below your body/skin temperature... say 75-95 degrees. When it gets to be 100 or above it's unpleasant no matter how dry. A 90 degree day in Denver isn't horribly uncomfortable compared to the same in New Jersey... but neither are anywhere near 115 in Phoenix. High dews are an annoying thing when the temperature is in the 80s, but once you get into the 100s it's more of a choose your poison thing. You might get heat stroke faster if it's 105 with a 70 degree dewpoint, but if it's the same temp with a 40 degree dewpoint you dehydrate faster.