weather question for a traveling newfoundland dog.?

you can easily get a vet note for temp under 45 degrees for a newfie because they can withstand cold weather............i would worry more about the temperature when you land in costa rica.........it also depends on how long the dog will be on the tarmac.........usually the cargo cabins are climate controlled for any animals traveling in there........i would be more worried about it being too hot than too cold.....newfies were bred to swim in cold water and bring in nets to fishermen and nowadays can be certified as lifeguard dogs......

Your dog should be fine in the cold but I would find out how long he will be there if they will tell you. It is more of a danger for him to be out in the heat when he gets to Costa Rica. Newfs cannot be out in the sun for long before they overheat and they need lots of water. I would find out how to make his stay at the airport there as short as possible and alert them that he has to at least be in the shade.