Dogs have a layer of mucus on their noses that not only aids their sense of smell, but additionally assists with temperature regulation. This can vary from dog to dog.
You may notice that if your dog is actively sniffing and awake, the nose is wetter. When at rest, their nose may appear dryer. The mucus on the nose is able absorb environmental chemicals. When the dog licks it’s own nose they are transferred to the olfactory sense organs in the mouth. It makes sense then, that if your dog is running around the park versus snoozing at home there will be a difference in how wet the snout is.
Whether the nose is dry can vary from dog to dog. Most likely you know your dog better than anyone else and what is normal for them. If you notice a prolonged change in the temperature, pigment or dampness of the nose you should contact your veterinarian.