The bullet is affected by wind the most right before the target. That is when the bullet has the least velocity and is dropping like a rock. One way to read it is to focus on your target and the back it off so you are focused on the heat waves in front of the target. If they are boiling straight up, no wind. If they are moving up at a 45 deg. angle, 2 to 3 mph wind. If they are going sideways, at least 5 mph. The last third of the distance is the most important.
Another thing I like to do is experiment with my wind meter
and see how far weeds bend or trees blow at different wind speeds. It gives you a reference when you see a tree blowing in your scope.