Albert Barnes Commentary 1 Samuel 12:17

"Is it not wheat harvest to-day? I will call unto Jehovah, that he may send thunder and rain; and ye shall know and see that your wickedness is great, which ye have done in the sight of Jehovah, in asking you a king." — 1 Samuel 12:17 (ASV)

Wheat harvest: This occurs between May 15 and June 15. The testimony of Jerome, an eyewitness, is that he “never saw rain at the end of June or in July in Judea.” This observation is confirmed by modern travelers.