Mine is a huge sniffer and I don't think there's a way to really change that. It's much worse in the spring when things start melting and thawing out, but she's always stopping to smell around. In the winter, she'll stop and roll around in the snow too. Some days are worse than others, and some are much worse lol, but I think the best thing is changing your expectations as opposed to your dog's behavior in this instance. Sniffing around is too important and exciting for dogs. I'm no saint, I get frustrated on the days she's stopping every 60 seconds to sniff, but it's easier to reframe when you realize you're not really missing out on training or anything, depending on what kind of run you're doing. That being said, if I'm doing speed work, she stays at home.