in winter lots of warm hay make the bunnies comfy, and in summer a cold pack wrapped in a cloth

i have a rabbit, and we give her lots of hay, and put it in a sheltered area, we let her run too, and if it gets too cold, she goes in the garage, but i recommend lots and lots of hay and staw, (hay is better for them tho)

You can make a well insulated shack based on slightly modified "doghouse" plans ... you can even get ritzy and add an electric blanket or heat lamp (be sure they can NOT chew the cord) ... but the easiest is to just drop a bale of hay and cut the strings, let them arrange it the way they want.

as long as they can get out of the wind, and have a relatively small, enclosed place with Hay (as other recommend) bunny should be fine... they live in holes in the ground, usually... You could throw a blanket over the hutch on sub-zero nights, or move into garage or basement. But, they don't need a heater...

little rabbit fur coats?

If you have the bottom of the cage covered with wood, etc. it will keep the cage warm. Also, you can use plexie glass, (you can get it at Home Depot) so they stay warm, but don’t get claustrophobic. Just think, if you covered it with wood, how awful it would be. I mean, would you like to stay in a cold, dark room all day? Also, if you do put wood under the cage, make sure that there is a good 1-2 inches between the cage and wood. You want to make sure that their droppings and urine don’t get trapped in an uncirculated cage. If the wood is too close to the cage the bunny will get wet from its urine and can get sick and die. Make sure the cage is 2-3 feet off the ground. You can also put cheap hand towels in to keep them warm. I sewed two dish towels together, (that I got at a local .99c store) and stuffed it with hay. They love to crawl in them and lay on top of them. As long as they have plenty of food and water and receive attention from you everyday, they are usually fine.

No drafts and dry are the two things that will really aid in keeping your rabbit happy outside. It can have fresh air but not drafty windy air. AN enclosed building, even a garage with lights is a good place. If the are outside in a cage, be sure that a draft doesn't come up from the bottom of the cage, though we have kept rabbits outside in 0° weather with wire cages in a pole barn and they had open bottoms. But there was no drafts and no rain getting in. They had lots of hay and fresh water twice a day as it will freeze in the crocks in those temps. We feed more hay because the pellets need the rabbits to consume more water to digest the pellets. So they get mostly hay and veggies during the cold months. If you have a nestbox for them, some like to hide in there but we haven't noticed any great difference in their happiness or health with them. I think it makes US more comfortable:-)

Why not send them on all expenses paid trip to somewhere tropical with white beaches and stuff

Big NZ rabbits like it outside, better than the basement. Rabbits NEED LIGHT and ventilation, and do better out in the winter than they do in the summer in MI. Only took them in for the below zero days. More concerned about above 85 degree days. Use plastic or cardboard to windbreak cage. If a blizzard comes, Give them hay and food and drop a tarp over the whole cage. Give HAY or Straw to hide in and keep them off the wire. I use hay so they can eat it. Do not use metal nest boxes in subzero weather. They avoid them, sensibly. Made a nice nest box out of sturdy plastic box that was 20 by 10 by 4 inches, and put a smaller cardboard box in it sideways like the top of a baby carriage. Filled this with straw. It will be a mess and need to be cleaned out, but right now the rabbit seems happy. Rabbits need fresh water often, twice a day in severe cold-once a day when they can get to snow. They love eating snow in 25 to 35 degree weather, and will eat any snow that drifts into their cage. I thought they liked keeping their cage tidy, but now I know they like snow. In the winter you need two water bottles for each cage, one for water-one to melt in the house & refilled hot. Baby rabbit survival actually is better in the winter. Rabbits die from heat, and dirty cages, and bad ventilation. In the winter, the air is clean and the cage sanitized by frost, and they know how to keep babies warm just fine.