Unless you live in a frost-free area, you must be careful about the shape of the terracotta pots that you use in winter. Those that curve inwards at the top should be avoided. If frosts come and the compost is wet, it may expand as it freezes, and break the pot. In a slightly flared pot, on the other hand, the compost will be able to push upwards and out, and there should be no harm done. Drainage is especially important during the approaching wet months, as plants can be killed when their roots sit in overly-damp, cold compost.
Put at least a five-centimetre layer of crocks (bits of broken pots) or other material in the bottom of each container before you fill it with compost. Check the compost in all your pots every couple of days to ensure that it is lightly moist. Although it may rain, the wind can dry a pot's contents out in a very short time.