I put mine outside at around 5 or so weeks with no heat lamp. They are fully feathered at that age and no longer need a heat lamp. They can huddle or pile for warmth if its cold and smother each other and corners is where they usually do that. I think that is what r2elk meant. You can remedy this by adding roosts and checking on them at dark and making sure they are all on roosts. Turkeys instinctively want to roost so you may not have any problem, just watch them. It has been as low as 40 at night since I've had mine outside and they've done fine. They have a covered pen and it stays dry.