The Kings of Leon frontman announced his engagement to the Victoria's Secret model in September 2010 but said that the couple have purposely kept the exact date of the ceremony under wraps.
"You have to ask Lily [about the wedding date]. She won't tell me. I think it's somewhere between May 10 and May 20, but she won't tell me because I have a big mouth," he told People.
Caleb's brother and bandmate Jared revealed additional details about the nuptials, adding: "It's going to be a very small wedding and then a big party. I think there are only like maybe 25 people or so going to the wedding, but a lot of people will be at the party."
Followill and Aldridge began dating in 2007.
Kings of Leon guitarist Matthew Followill recently announced that he is expecting his first child with wife Johanna Bennett later this year.