Temperature and Hibernation
Hedgehogs are native to warm climates and cannot tolerate the cold. If the temperature drops below 65 F then a hedgehog may begin to show some symptoms of hypothermia (often called hibernation, even though African Pygmy Hedgehogs are unable to hibernate). Some symptoms of this are becoming lethargic and being cool to the touch. They will be slow responding or even not responding. If not reversed, this is fatal!
Hedgehogs need to be in a room that is in the 70's year round. We have central air and this has been tricky for us. They sell heated pads that can be placed under the habitat, but we feel that having the room warmer is the safest bet.
We ended up purchasing a Diamond Infrared Heater that is programmable and can be trusted to be ran 24/7. Our Hedgie Room is kept 76-80 F. We also have a dehumidifier set to 45% humidity, and have a fan that controls the air-movement in the room.
If you notice that your hedgehog has become cool to the touch and seems to be having difficulties moving and/or has not been eating then immediately get it to a warmer area, and bring the temp up very slowly, at least over 20 minutes and contact your vet.