My leopard will wander out if the door is open but soon turns around when he realises how cold it is. I don't usually let him outside unless the ground temp is at least 70'F just to be on the safe side.
This is when you the care giver needs to know what is best. Leopards are not familiar with snow or the cold temps that go with snow. They don't have that instinct of winter as they don't live or come from a cold snowy place.
I would not let my leopards outside in the snow!
And tortoise are not like dogs and they can not tell you they want to go out.