Outdoor containers made from terracotta or pottery need to be frost proof to avoid cracking. It is also advisable to lift them off the ground so they do not freeze to the path. A hard frost can see the base left behind when the pot is moved. To prevent this you can buy small pot feet, put the container up on bricks or stand it on some gravel or bubble wrap.

Winter Container Care Tips
Keep winter containers out of cold drying wind for the best results. Any shelter will be appreciated by plants that have to do battle with winter conditions.
Winter can often have dry spells so keep an eye on pots that may need some watering. This is also true of pots under roofs and eaves.
I like to use a woooden tub or half barrel and start by lining the container with a few bits of broken flowerpot or polystyrene for drainage.
Plant pre-grown bulbs before adding the other plants with trailing plants at the edge of the container. You can bury small pots in a larger container and change them as necessary.
Plants grow more slowly in winter so pack them in fairly close together to get a quick effect.
If you have special plants that do not like their crowns to get wet put a glass cover over the pot.