The caruncle drops off a few days after hatching. The hatchlings have a keeled shell and an abdominal fold, both of which disappear as they grow. Their shell pigmentation and markings are brighter and more pronounced than those of adults. They mature about five years after hatching and are thought to live as long as 20 years. Wild hatchlings may over-winter in the nest.
Adult painted turtles are also cold tolerant, and have been observed swimming under ice.
Most painted turtles become dormant in the colder winter months. They burrow into the mud of their pond or seek muskrat burrows or other suitable shelter. While dormant, their need for oxygen is greatly decreased, and they can absorb sufficient oxygen for their needs from the water through their skin, throat linings and thin-walled sacs in the anal area. The more northerly subspecies brumate regularly and for a longer period than their southern cousins. It is possible that southern and western painted turtles living in the most southerly reaches of their ranges do not brumate.