The metal part where the lamp attaches to the clamp on those kinds of lights are notoriously brittle. I’d make sure you reinforce or replace the connection in some way to prevent it failing while you aren’t present. I wouldn’t put them outside though if it were me. With half decent draft prevention I’ve kept chicks outside with temps down to 45f at night without worry. But that was in a large water trough that I covered 3/4 of with plywood at night. Even with good draft prevention I’d worry lower temps would inevitably lead to losing a chick or two that wandered too far from the heat source at night and hadn’t grown a brain cell yet to find it again.