Depends on how cold your winter season is, grow anything in the cold is not very ideal, as the winter weather can damage the plants and affect the health of the plants growing in them. Cold temperatures, frost, snow, and freeze-thaw cycles can all cause plants to suffer. If you want to continue growing plants in grow bags through the winter, it is recommended to move them indoors or to a greenhouse where the temperature can be controlled. 247Garden offers greenhouse plastic that you can use to protect your plants from harsh weather.