Hi, I haven't posted in here for ages but thought your two queries deserved a reply. Hope I can help. In general yes ferrets do need time out of their cage and if you can find a sitter who is confident enough to let them out that would be better but don't worry too much if it si only for a short period, no more than a few weeks, it won't actually do them any harm.
As for keeping them outside it depends really on your climate. In the UK, where i live, most people keep their ferrets outside, mine have a large outdoor cage and come into the house to play. Our minimum winter temperature is probably about -8oC and max in the summer about 30 oC . Their cage is in a sheltered spot so I don't suppose they actually get those temperatures.
In the winter they are fine so long as they have a secure area to sleep in with plenty of hammocks and blankets, if I put my hand in to check they are always warm. In the summer I am more worried but they have a shallow pool to paddle in and some people freeze bottles of water for them to lie on.
Hope that helps a litle.