Fire, and hail; snow, and vapour; stormy wind fulfilling his word:
Fire - lightning.
Vapour - the result of fire and water together. Hengstenberg translates, 'smoke;' the dark smoke contrasting with the white snow (Psalms 119:83; Genesis 19:28).
Stormy wind fulfilling his word - (Psalms 147:15.) However the stormy wind, with its wild impetuosity, may seem reckless of all law, it still is executing the word and will of God no less than the angels, who "do His commandments, hearkening unto the voice of His word" (Psalms 103:20).