and about a rabbit staying outside, in winter always make sure the rabbit has a lot of hay to make a burrow in, you may need to change the water bottle or bowl, whichever you use about 3 times a day as it will freeze if it gets cold enough, i prefer to fill my water bottles with warm water. as for keeping the cage warm, there is plastic that you can buy from home depot or lowes, it is kind of thick and you take what ever size you need to cover the sides of the cage, you should use a staple gun to apply the plastic, and you dont have to cover the bottom of the cage. you also may need to acclimate the bunny to the outdoors if he is indoors. also, very important... if you want to take your bunny inside when it is very cold, you dont have to worry about the bunny being cold, but if you do take him in only do that for about a half of an hour maximum. if you take your bunny inside when it is cold you have to keep him inside until it warms up again because the temperature difference could make him get sick. so it really isn't a good idea to take him in during winter but you can take him in during the other months. also when it starts to et warm again you can pull the platic right off the cage and throw it out or keep it depending on its position. also if you pull it off sometimes there are staples still in the wood of the cage to limit that possibility you can put duct tabe on the plastic where you are going to put a staple, this keeps the staples from staying in the plastic.
you may or maynot already know this but during the hotter summer months bunnies can get heat stroke, so if you see that the bun is all stretched out or breathing heavy you can freeze regular water bottles and put them in the bunnies cage to help him cool off. when you give him his drinking water bottle you should put very cold water in it and if possible you can put ice cubes in it too. dont give too much hay in the summer, just enough to lay on and have some in a rack hat he can eat. you can also buy salt licks from the petstore and the bunny will chew on it.
trust me about this information because i have had many rabbits outside year round and have done this many times. if you have any questions PLEASE ask.
ani-lover