Dougt from Onawa, Ia. on 8/11/2020 5:29:59 PM:
If you Google it, the prevailing winds in Valentine are from the south until the end of Sept.
My brother and I are doing Norfolk/Valentine and back late Aug so I'll post an update on the thorn and trail situation. I did it two years ago and never saw a thorn, then we did it last year and had a multitude of flats. Thorns always seem to be from Ainsworth to Valentine.