Elijah was pressed to show that Yahweh, the god of Israel, was powerful enough to deal with the current drought -- as people were turning to the Canaanite god, Baal, who had gained a reputation as a fertility god. Elijah proposed a contest to demonstrate which god was supreme. Prophets on both sides would call upon their god to send down fire to the altar, and the one who did would be the real god.
Here we see the altar, made of twelve stones representing the twelve tribes of Israel. The wood is laid out, water has been poured on it, and Elijah is already beginning to spread his hands in the gesture of prayer.
In the end, Yahweh was the one who sent the fire. But more importantly, a tiny cloud is beginning to form over the waves of the sea. Deliverance from drought is on its way even as Elijah begins his prayer. Yahweh demonstrates that he is God, not so much in the sending of the fire, as in the sending of rain, and in the salvation of his people.