First, you'll need a warm blanket: fleece is a good material since it dries quickly, is easy to care for and fairly inexpensive to buy. But any old blankets will do,( note I only put the blanket on at night, the plastic cover will do for the daytime in less you are in really cold conditions).
You'll need a waterproof layer to go over the blanket. At the moment I'm using an old sheet of plastic, if you had a standard hutch then go ahead and buy the covers supplied. They're not the best quality, I have to say and they are pretty pricey for what they are.
But if you don't have a big budget to spend on the cover, follow my example and find an old sheet of plastic or go to a hardware store and buy one.
I also bought a rabbit heat pad, which I warm up in the microwave and pop it in their hutch when it is below zero, you can find the rabbit heat pad in most pet shops.
I can't do this with my hutch, but if you can relocate your rabbit hutch to a more sheltered spot, it can help to keep your bunny nice and warm during the winter months.
If you have a standard rabbit hutch, it is even more important for you to keep the hutch dry since the hutch is made of poor quality wood and will easily get mouldy. If you start to see mould growing on your rabbits hutch this is a sign that you need to change the hutch.
There are a few things to do if you wish to prevent this on a newly bought standard hutch:
Find some kind of waterproof sheet and staple it all around the hutch. Make sure to check regularly behind the sheet since mould may grow in between the sheet and the back of the hutch.
Make sure that the hutch is in a sheltered area of your garden.
Treating the hutch with some kind of waterproof paint may help but you have to take in to account that your rabbit will probably chew their hutch.
My best tip is to have someone make you a custom built hutch since they are much better quality than standard hutches these however are expensive.
I will be doing a post on how we built our rabbit hutch soon.
Have a question, would like to request a post just comment below and I'll do my best to answer it.