Rashi: He makes the winds his messengers. Radak - nothing is chance; everything is with intent.

Malbim: There are two catalysts to explode clouds and make rain fall - (a) wind, and (b) an electric substance of fire found in vapors. When the fire comes out, there is thunder and lightning, and the clouds explode and rain falls. The Mal'ach is the messenger that goes from place to place. He makes wind His messenger to take the clouds to their places.

Radak: It is fire and lightning that go rapidly. Everything is with His word and command.

Malbim: It is the heat and fire stored in clouds. They do the work of [making] rain. When the air pulls the fire of the vapors out, they gather and empty rain onto the land.