Mine are in a Pighouse (wooden playhouse that DH customised) so they have a haybox to sleep in and the floorspace and added play/hiding spaces, but all enclosed.
In good weather, we take out two of the windows (the window soace is re-inforced inside with metal mesh,fly mesh and wooden 'bars' to protect them) which gives ventilation.
They have a fan to waft a breeze if they need it.
I wouldn't leave mine out all winter, more the damp and continual dark I think. They can cope better with cold if they are well insulated but it needs to be dry. Though they tend to just sit there in the hay which is no fun for them, really.
You can get thermal waterproof covers for most hutches.
I use loads of different things, sometimes depending on what I have.
In the Pighouse, I have (on the wooden floor) rubber car mats/ boot liner; an old oilcloth tablecover and a tarpaulin to cover the floorspace.
Then cardboard
Newspaper
Soft straw (has to be soft pet straw, not equine)
In their haybox they have wood pellets (rodent safe cat litter) under newspaper, topped with deep hay
In the indoor cage - woodpellets , a layer of newspaper and a piece of fleece or an old towel.(If I'm throwing them out)
I don't wash them, they get thrown out . The fleece costs me £3, I get six pieces. Not worth the risk to my (elderly) washing machine for 50p worth of fleece.
We feed our morning/evening. At breakfast, I check them all (just say Hi Pigs and make sure they're al mobile and look ok) at night they have a cuddle and check.