Have you noticed how in cold weather your dog takes much more time to sniff everything? It can be annoying if you are in a hurry to get along but your dog needs to take time to read all the local information. The reason your dog takes so long in Winter is because the scents do not smell as strong when the weather is cold. During warm or hot weather the molecules in the object of the sniff (a pee from another dog for instance) will be moving and going around at high speed. These items of scent are called 'volatiles'. Think of your hot cup of tea or coffee for instance. The heat creates volatile substances that rise at high speed into the air... you know it as steam. But in cold weather the volatile scents are hardly moving at all, and it is these volatile scents that your dog is sniffing for. So in cold weather there is hardly any scent coming off the object that he or she is sniffing - hence, they need to give it a jolly good, long, hard sniff to find out what it is. Give them more time please! don't just pull them away.
I was born 20 yards from our allotment. My parents used to 'dig for victory' and never got out of the habit. I grew up on an allotment, so growing veggies is a way of life. I am also qualified as a dog behaviourist and I have set up my own business, www.blackdogdna.com