A mortgage lender can foreclose at any time of year if they have properly followed the state’s foreclosure procedure. A borrower in default receives notice of the foreclosure sale well in advance. Furthermore, even after the house has been foreclosed, the occupants have some time to move out.
In recent years, major banks have elected not to foreclose on people in December since it is close to the holidays. It can create bad press for a lender to foreclose on a family right around the holidays. Some lenders will delay December foreclosures until January.
Some states have laws about eviction of families with young children in the midst of winter. Some state laws extend the time period for a family to move out during the winter months.