Albert Barnes Commentary 1 Kings 18:1

"And it came to pass after many days, that the word of Jehovah came to Elijah, in the third year, saying, Go, show thyself unto Ahab; and I will send rain upon the earth." — 1 Kings 18:1 (ASV)

The third year – that is, in the third year of his sojourn with the widow. The entire period of drought was three and a half years (Luke 4:25, James 5:17). Of this time, Elijah probably spent about one year at the brook Cherith and two and a half years at Sarepta.