Some forms of Chinese cabbage are as cold tolerant as typical cabbage.

If you have the plants in at least 4-6 weeks before your worst frost, they'll do just fine.

Joe

The Chinese cabbages are somewhat frost tolerant but will show damage in a freeze. This is especially true if the foliage is kind of wet at the time of the temperature drop. To be on the safe side, have some covers, not plastic, available to toss over the plants if temps go much below just a touch of frost.

Even if the heads aren't fully formed, they will still be nice for salads or slaws.