Maybe this is a silly question, but I'm new; What happens when it's kept inside and warm, 70F, but it's
-5F outside. Won't the bees try to fly and freeze?
No, they go to the door and stick a finger in the air and if it develops frost on it they don't fly.
Regardless of the temperature inside the hive whether the bees chose to fly or not is dependent upon the weather outside the hive. I've found that they will occassionally fly in temps in the mid-30s and overcast with a slight wind. Lower than that or more wind and they stay home. As for the hive itself, it is the temp of the air around the cluster or brood nest that determines whether they remain in cluster or break it up. That means that if the internal temp of the ambient air within the hive is in the mid 70's the bees most likely will not be a cluster but whether or not they fly is still up to outside conditions.