I would guesstimate the same as a low-to-middle sized hill
I have found that crosswinds are worse for control
my haro was very light and I would get tossed all over, but my deviate is a tank and hardly notices
One day, I had a headwind from the North that was so bad, my bike wouldn't accelerate over 20MPH. In fact, it was so strong that it was interrupting the intake!
If I turned the bike at any direction other than North, it would accelerate, but at North it seemed like it couldn't get any air in the intake. This was with the stock "4-hole" plastic airbox. Needless to say, turning South made that bike fly!