Humber earned three Texas Little League state championships. He subsequently attended Carthage High School in Carthage, Texas, where he led the baseball team to the state championship game in 2001, his senior season, winning state Player of the Year honors. He then attended Rice University, where he played college baseball for the Rice Owls baseball team. Humber was the winning pitcher in the clinching game of the 2003 College World Series. He has also represented the United States at the World University Baseball Championship.