The thread on what is a 1-club wind got me to thinking. How do you gauge the wind? How do you determine if it is 5, 10, 20mph, etc? Obviously that is critical in determining if you need one or more clubs playing into it. Tahoebum uses a formula, 1% for each mph. Can anyone tell the difference in even just a couple of mph? Do you use an app while playing? Is it how the flag or trees are moving? The weather forecast before the round? Experience?