People often ask if they can leave their Ollas in the ground over the winter.
My general reply is, "If you live someplace where the ground freezes, NO, because they may crack."
Like terra cotta pots, Ollas absorb (and transfer) water . . . so leaving them in the ground through freeze-thaw weather cycles could cause cracking as the water in the walls of the Ollas freezes and expands.
But Ollas may be a little tougher than I though . . . I've left 3 Ollas buried in our gardens here in Wisconsin last winter, and all of them this winter, and they have all survived just fine.
One is pictured above. As you can see, it has heaved out of the soil a little this year, but it is not cracked.
We will likely dig them up and rebury them deeper this spring, and I would still recommend that you dig them up if your ground freezes in the winter . . but they may be more durable than I thought.