Back in the mid 70s, we were conducting an external load lift of a 105mm howitzer in the Norwegian mountains. The indicated OAT was -44 degrees C. The recirculating snow was an issue but dissipated quickly although much blew into the cabin through the open doors. My lasting memory is of the crewman using a brush to clear the snow out of the door. The joy of operations in such cold temperatures is that the snow does not stick. Engine and airframe entirely happy but not sure about the PUMA HC1 ODM.