What are the results of preaching and teaching the Word of God in the open air?

Let's define results.

From God's perspective we live in a dark world. A world of sin and death.

The Word of God is Light and Life.

The results of open air ministry are centered around the goal of bringing the Light and Life into an area that is dark and dead. The Church's job is to bring this Light and Life into areas that are dark and dead.

As you know when the Light and Life of God is brought into an area It produces results.

You have to value that the Light and Life of God are being brought into an area that is dead and dark. If you do then you rejoice (Phil 1:18) whenever and wherever the Light and Life of God are proclaimed.

Thus the results of preaching and teaching the Light and Life of God in the open air are pleasing to God as He desires His Light and Life to be proclaimed throughout the world.