Albert Barnes Commentary Psalms 147:18

"He sendeth out his word, and melteth them: He causeth his wind to blow, and the waters flow." — Psalms 147:18 (ASV)

He sends out his word— He commands: or, he speaks.

And melts them— Melts the snow and the ice. Compare the notes at Job 37:10-12: “By the breath of God frost is given,” etc. The idea is that they are entirely under his control. They obey him when he speaks.

He causes his wind to blow— The warm south wind: his wind, because he directs it, and causes it to perform his will.

And the waters flow— The snow and the ice melt.