There are blessings for all sorts of occasions. On seeing a rainbow in the sky you say, "Blessed are you God, King of the Universe, who remembers the covenant, is faithful to the covenant, and keeps his word" (Shulchan Aruch, Orach Chaim, 229:1). One should not, though, look at the rainbow for too long; it is as if this beautiful sight is an intimate sign between God and humanity.
The blessing refers to the first rainbow that we know of, which appeared after the Flood. God promised Noah then that the rainbow would be an eternal sign that He will never again destroy all of creation. This is despite the continued existence of wickedness on earth since.
But, reflected one of my rabbis, "the sign of the rainbow does not guarantee that humans will not bring destruction on ourselves". With the increasing likelihood of humanly caused climate change, where does God's responsibility for disastrous weather events end, and ours begin?