Much depends on the terrain. Here in Texas, some flying feilds have no trees and no obstructions to interfere with the moving air mass. In those conditions, the air mass remains laminar all the way to the ground. Essentially, its just like flying in no wind at all. However, if there are trees or obstructions within 5 or 6 or 7 hundred yards of the runway, these obstructions will cause the air mass to be turbulent. In turbulent conditions it is more difficult to fly.

For scale models, I fly in 10 to 15

Sport models up to 20

Some great sport models fly well in winds up to 30 or 35