A golden has a double coat for a reason: It protects them in the cold and the heat.
There is absolutely no need for a coat.
The best rule of thumb in cold weather is: If there is a cold advisory for humans then it applies to dogs. Don't keep them outside for a long periods of time when it's extremely cold.
And in general dogs who are active in the winter do tend to lose weight. I have to normally up my guy's food in the winter so he doesn't lose weight.
The one part of their body that needs extra care in the winter are their pads when there is ice, snow and salt on the sidewalks when you walk. Be sure to wash off their pads with warm water and dry them after a walk. There are products to put on their pads before going for a walk to protect them from the salt.
I have to disagree with you Rhondas. My girl wears booties and a coat in certain situations, even though she has a double coat and it is absolutely necessary! Generally the situation is when she is coming on a AT skiing or telemark skiing or mountaineering trip with us. My girl has a lovely double coat, but it's just not enough to protect her when she is out in the snow spending multiple days running or walking after us or watching us run laps on a good line.
I am sorry to say I am not a fan of the rule of thumb for cold weather. We are not going to exclude her, by leaving her home just because she could get cold. There are many risks associated with the being out in the elements and the solution is within your risk management. Yes my girl is at risk being exposed to cold weather and the elements, but we plan for and manage these risks. We do always carry multiple layers for her depending on the weather and have even set up camp early if she was getting cold (she quickly warms up in the cosy tent with some food in her belly and a down sleeping bag over her and human to cuddle!). Often if we are doing multiple runs on a hill we will dig her a little cave and insulate it for her so she is protected, warm and can happily nap (unfortunately my lab top AC socket is broken, otherwise I would post some cute photos of her!).
We have even butchered our expensive technical clothes one trip, when we were struggling to manage her temperature control. Food does make a large difference, we eat often when we are on expeditions and she eats every time we do (you wouldn't believe how heavy her food is, even with dehydrating it!). We also feed her a very different diet to keep her energy up. I have also noticed with age she is more susceptible to the cold.
If I was to not put our girl in protective gear, then I can guarantee she would suffer. She would become a huge liability, when the weather hits or we are fighting a long day to get to camp we need the assurance that she is protected and safe, also it would be cruel. Also because we are 8 hours away from snow it can be a shock to her system to go from mild winter weather to the extremity of the mountains, making protection for her even more vital.
So do you think that I shouldn't be putting protective layers on my girl? I am glad to hear your a fan of booties. Do you think that I am considered a bad owner for taking my girlie into cold weather and that she should just be left behind.