Notes on wind velocity:
1-3 mph will move dry tall grass
2-4 mph - you can just feel on your face, large leaf, light stems (like maple leaves) move
4-8 mph - will make small leaf, heavy stalks (like alder) move
5-6 mph - flat-lines a 24" piece of flagging ribbon
6-10 mph - will move the tips of short needle trees like larch & spruce
8-12 mph - will make brush like alder, small aspen etc start to move
10+ mph will make trees start to move
5-6 mph - mirage tips 45 degrees
10 mph - mirage starts to flat line
Open air moves faster than air close to the ground, if you are on a canyon wall and the wind is 10 mph it is a pretty safe bet that in the open of the canyon where you have to shoot across it will be 25-50% stronger.