The arrival of the little cloud occurred in this way, as described in 1 Kings 17 and 18. When the wicked King Ahab and his even more-wicked wife Jezebel ruled the northern kingdom of Israel, Elias (Elijah) prophesied to the king that a drought would come over the land.
"As the Lord liveth, the God of Israel, in whose sight I stand, there shall not be dew nor rain these years, but according to the words of my mouth" 1 Kings 17:1.The drought was in retribution for the fact that pagan Jezebel had led Ahab away from the worship of the true God. Together they had torn down the altars to the true God and kept hundreds of pagan priests on their payroll, who erected altars to Baal and worshipped the false god throughout the land.
A "grievous famine" then fell on land of Samaria, and "after many days," the Lord told Elias that He would again give rain. Elias rose up and left his place of refuge and engaged the prophets of Baal in a showdown. (You can read about the showdown in 1 Kings 18.) After Elias defeated the prophets of Baal, he "went up to the top of Carmel, and casting himself down upon the earth, put his face between his knees, And he ordered his servant: 'Go up, and look towards the sea.'"
When the servant went up on Elias' orders and looked at the sea for the first time, he came back and told Elias, "There is nothing." Elias told the servant, "Return seven times."
When Elias's servant went back up to look for the seventh time, he glimpsed a little cloud without blemish, the size of a man's hand (1 Kings 18:44), rising out of the sea.
The arrival of the cloud was a welcome sight because it meant the rain was coming, as God had promised Elijah it would, to relieve the long drought. The Church also understands the little cloud without blemish as a prefiguration, or type, of Mary, the Virgin Mother of God, who would relieve a longer drought. In the same way the cloud rose up out of the sea without any of the sea's impurities, Mary rose from among the human race without any stain of sin.
Her son Jesus was to be the long expected Savior promised to Adam and to Abraham and to Moses. The drought can be seen as the separation of the human race from eternal life after the sin of Adam and Eve. The birth of His Mother, who was conceived without sin, was a sign that His coming was near and the drought was about to come to an end.
Thanks to Fray Eric for the original photo of Mount Carmel that I cropped for this blog.