Still rather cold, plenty of frost and the odd day of snow.
Sunny days can dry up the trees quickly so the need to be watched, also the winds dehydrate very fast.
However this year [2007] has been very wet so there is more chance of root rot through water logging than there is drying out!
Towards the end of Feb watch the trees, as soon as you see the buds starting to swell it is time to consider re-potting.
You need to protect the tree from wind and frost after potting so ensure you have enough sheltered positions.