They now believe in the True God. Pharaoh still refuses. So Moses stretches out his hand holding his rod and a strong east wind begins to blow. It will blow for almost a full day and night. The next morning the locusts come.
Locusts can only fly for very long if there is a wind.
This alone demonstrated to the Egyptians that God was over the world, not just over Egypt. The locusts eat everything that was left by the hail. They eat every green plant. They eat all the fruit off of the trees. There are so many locusts that the ground cannot even be seen.