He can probably handle those temps, but it's not right. A blanket gets wet and doesn't provide much warmth. If it's windy or wet he's got no shelter from that. Plus Goldens are very people orientated dogs. They need to be their with their humans. A puppy especially needs to be with people in order to get socialized properly and not develop behavior problems when he grows up. All dogs need human contact, but some breeds need even more than others. A husky can be fairly indepedant for example. I've never met an independant Goldie! They are happiest curled up beside their family.