Here is my 2 cents...
I may be wrong, but for me & my equipment, here is my general rule of thumb wind speed formula:
1 mph of wind equals around 1 foot of travel. Example; an 18 mph head wind coming straight at your 6 o'clock equals an additional 6 more yards. If the wind is say blowing 9 mph at 2 o'clock (slight tail wind), then you would subtract about 2 yards from the club being used.
I hope this helps, and please comment if this is what others experience as well.
Trackterror03