How temperature affects show rabbits
Rabbits that are for show are very heat sensitive depending on the breed. In the wild rabbits ears grow larger because they act as an air-conditioning unit for the animal. If you have a breed of rabbit that has a strict maximum ear length remember that the hotter it is, the more the ears will grow.
If you have a Netherland Dwarf (whose ears should not exceed 2 1/2 inches) and its ears are one inch over the maximum, do not start blaming the Texas weather. Most of it is probably the genetics of the rabbits, but some of it may be related to hot temperatures.
There are an enormous amount of disqualifications a rabbit can have at a show. While most of these are based on the lineage of your rabbit, there are a few that you can control. Smut is a discoloration of the fur that is associated with a few breeds. It generally occurs because the rabbit has come in contact with cold wire (a common cage material). Smut is will not harm anything other than the color of the animal, so it is common to have smut on rabbits that are used just for breeding.
It is up to your discretion as to what temperature you believe your specific herd can stand before smut starts to occur. In my case, anything other than 47° means the cage is going to be lined with straw or hay. This will reduce the contact the rabbit has with the cold wire.
With all this in mind 65° should be the perfect temperature for your animals to thrive.
Other temperature concerns: