You don't ever want "no humidity" in your incubator at any time no matter where you are. The difference between dry climates and climates with more humidity is we (higher humidity) can usually run (depending on the season) "dry" and still have a decent amount of humidity in the bator whereas you, or dry climates will have to add a touch of water or a wet sponge to get the same results. Low humidity incubation, in my opinion is anything between 25-45% percent. Anything higher than that, IMO is standard incubation process and for the most part sucks. Anything lower than that for the average of the incubation is risky to me. It is normal to see the heat raise a degree or two at the end of the incubation (if you aren't using an incubator with a thermostat, because the chicks have started to produce and give off their own body heat. People with thermostats don't see it because their incubator automatically adjusts for the heat, those of us that have to play thermostat ourselves have to adjust for it.
Yes, elevation does matter and higher elevations actually need HIGHER humidity.
http://www.thepoultrysite.com/articles/2908/incubating-eggs-at-high-altitudes/
No I did not. I usually do if they have it listed, (not that that means I know the topography of the area...lol,) but it's something that I don't take into consideration enough when talking about humidity.
"Occasional" hatching......