I read they don't but they hunker down in there underground dens:
Where Do Chipmunks Go During Cold Weather?
Chipmunks spend spring and summer building tunnels that extend deep into the ground. They collect enough food to last several months and then move to the lowest chambers in their burrows.
When Do Chipmunks Hibernate?
While not in true hibernation, chipmunks do enter a state of rest to conserve energy. From late fall to early spring, they spend the majority of their time sleeping underground. On warm days, chipmunks may wake to forage for food outside.