In this verse, meteorological phenomena are mentioned, which are visible when one looks up.
Fire
is lightning. It is said of those powers in nature that they do what God says.
There is no call to praise here, but a motivation for it. It connects with Psalm 148:7, as it is about forces that dwarf humanity, while their Maker can do with them whatever he wants. They are obedient to God. In that, they are in fact doing what is required of them, magnifying God.
8 fire and hail, snow and mist, stormy wind fulfilling his word!