"That’s Mike’s project," the star, 27, said of her fiancé, hockey player Mike Fisher. "It’s a surprise. I have no clue where we're going, which is nice."
There's only one requirement: "I know it will be warm, that's it," she told reporters backstage Thursday at the concert in Nashville for CMA Music Fest.
Underwood is similarly relaxed about the couple's gift list, saying they are forgoing a wedding registry.
"We just want people there – that’s the best gift," she said. Of course, "the basics are always nice, like a nice bottle of wine. We can write your name on it and when you come over for dinner, we can break it out. "