Cracking/delaminating clay pots is pretty common in the winter. They are porous, and water gets into them and you get freeze/thaw. Whether the crack or not depends a lot on local conditions, especially what's IN the pot. Empty pots do a lot better. Did you recently water them before this happened?
When I was a kid, my mother made me winterize all her clay pots by transferring the plants out of them, cleaning them out, and wrapping them in bubblewrap to keep moisture out. They're OK to freeze, as long as they're not wet.