Sandi, In plastic pots, I would place them on the ground in a place sheltered from the wind, then water occasionally (and lightly) a bit with cold water when the temps are above freezing (Put the water jug outside for a few hours and if it is not freezing the water, then it is OK to water a bit). You could also cover them to shield them from the wind, but not with plastic. The issue for me has always been them drying out in frigid winter winds when there is no moisture.
Another strategy would be to sink the pots up to the rim in the ground and water the ground around them. A cover, such as an old sheet, would not hurt.
Proximity with the ground does help to keep them from drying out.
Having said that, each climate is slightly different, so you will need to see what works for you. A few minor losses are inevitable, but we get better as we learn the local needs.
