I've always read that about 82 degrees is the absolute highest they should be subjected to. Some ferret do overheat at lower temperatures than others for other health reasons; some can tolerate more towards 85, but 80 degrees is just about safe for everyone. If your ferret has a heart condition, is overweight or is older (age 3 or older), or has other health problems, they will probably overheat faster. I think your 80 degree limit is a very wise and safe one. I have an alarm in my home that i can set so that if the temperature gets to a certain level, it will call my cellphone and tell me there is an emergency at home. I have that set at 82 degrees because I have fairly healthy ferrets. The device is called Sensaphone and I got it on eBay just in case you're interested in one. It was very reasonable and sure gives me peace of mind because I live in the desert and depend on an air conditioner. If I'm ever away from home and the air conditioner malfuntions or stops, i need to know right away and get them to a cool place, or I could lose my fuzzies.......so it's especially important. If you live in a milder climate, you probably won't hve to go to the extremes that i have to have peace of mind and still be able to leave the house in the summertime. The other thing folks need to be aware of is that a fan will NOT cool your ferret. In order to cause cooling with a fan, another element is necessary - cooling is caused by water evaporation, so if you are planning on using a fan for your fuzzy, be sure to wet down the blankies in the cage, keep a big tub of water that your ferret can get in and stay wet, OR use a misting system (available at any patio or home store) and a fan......there are options, but ALL that are effective will require movement of air AND presence of water on the skin (soak them all the way down to the skin, not just on the outside of the fur for best cooling). Every ferret's tolerance for heat varies and is affected by the ferret's overall health, age and weight. While panting is normal for most other animals as a means of cooling, when a ferret begins to pant, it means you have a heatstroke emergency and MUSt cool the ferret down immediately or you will lose him. Don't stick an overheated ferret into 'cold' water, as it is just too much of a shock....rather, use lukewarm water and circulating air, then slowly cool the water to a cool (but not cold) temperature and be sure to get the ferret to an atmosphere with lower temperature immediately afterwards, or he will be right back in the same condition as soon as the water on skin/moving air combination is removed. When taking your ferret to the vet in summertime, plan ahead and pre-cool your car by running the air conditioner before you take the fuzzies out to the car. Make sure they are in an enclosure where the air conditioned air can flow freely thru it. Never ever, under any circumstance, leave your ferret's cage in full sunlight without someplace they can get out of the sun - direct sunlight can really make them overheat fast. When we travel in the car in summertime, I keep a towel over the top of the cage so the sun coming in thru the car windows can't 'bake' the furkids. Leave the front and sides open eough that the air conditioned air can move thru the cage tho. One last suggestion: Always touch the ground with the back of your hand and feel how much heat is coming off the sidewalk, street or ground before walking your pet in the summertime. It gets hot down there where they are - the hot ground can burn the delicate pads on the bottoms of their feet, and we don't notice beause of our shoes protect our feet. Always carry water with you in summertime when walking ferrets........ remember they are taking about 10 steps to each one of yours and they dry out quickly and are very very grateful for that cool drink during the walk. Just a small tupperware type container with water and an ice cube in it is perfect to stick in your pocket or purse; if you're going to be gone very long, stick in a baggie of food too! Ferret picnics during a walk are a lot of fun! Hopefully something here was of use to someone. Living in the desert makes us very very aware of summertime dangers. Just some suggestions from the desert - jacquie, kylie & gilbert yuma, AZ (where summer temps are over 100 degrees daily for months) [Posted in FML issue 4560]