I get quite a few weeks from Walla Walla but this is the right kind of country for that, I suppose.
First off, I'm only about 200 miles from Walla Walla, WA . . . WaWaWA . .

(crying over onions) Secondly, yesterday the humidity dropped to 10%. That isn't terribly unusual - humidity is often below 20% by the end of a summer day.
I have some onions curing in the backyard right now. They are on the board step to the greenhouse and out of the sun for all but about an hour at the end of the day. Seems to work to have them there about 2 weeks.
I'll get them to December without much in the way of problems, once they've gone down to shelves in the basement.
Steve