Reverse Gear Does Not Engage

1999 Ford Escort Wagon with automatic transmission does not engage when gear shifter placed in reverse. Problem started in past few weeks when really cold weather. Has not gotten any better since it has warmed up. Any suggestions would be appreciated.

Mine used to have trans problems when the weather changed, try changeing tran fliud

put some lucas transmison additive in it and if it dont helpthen id say it would be the band in the tranny has broke or slippin