Sonny Weems played basketball at West Memphis High School where he was named first team all-state as a senior after leading his team to the 5A state championship, and was also a 6-10 high jumper in track and field. In Weems' high school career, West Memphis posted a record of 68-10. Weems averaged over 20 points per game as sophomore and junior, and 14.0 rebounds per game as a senior.
After high school, Weems attended junior college at the University of Arkansas-Fort Smith, and was named 3rd team All-American, as well as all-conference and all-region as a freshman. Ranked as the number one junior college player in the nation by Rivals.com and Street & Smith's, Weems took UAFS to the National Junior College Athletic Association (NJCAA) National Championship in 2006. Weems was named Honorable Mention All-American and was selected for the all-tournament team. In two years at UAFS, Weems led the team to a 62-7 record and back-to-back Bi-State Conference Eastern Division titles. Weems signed with the Arkansas Razorbacks as a junior, which was also Stan Heath's final season as head coach. He averaged 11.8 points per game and was named to all-tournament teams at the Old Spice Classic and the SEC Tournament as he helped the Razorbacks to their third consecutive winning season and their second straight NCAA Tournament appearance, losing to the USC Trojans in the first round.
Weems played his senior season with a new head coach, John Pelphrey, and earned first team All-SEC with per game averages of 15.0 points, 4.5 rebounds and 2.6 assists. Weems led the Razorbacks to their first NCAA tournament win in nine years with an upset victory of Indiana University. He finished the game with 31 points, out-dueling the much heralded freshman Eric Gordon, who was held to only eight points. After his team lost in the second round of the NCAA tournament, Weems later won the College Slam Dunk Championship held at the Final Four.
Weems was selected with the 39th pick of the 2008 NBA Draft by the Bulls, but he was traded almost immediately to the Denver Nuggets for a second-round pick in the 2009 NBA Draft in a three-team trade involving the Portland Trail Blazers.