Plenty of dogs get through a British winter without a jumper. A thick double coat, like a Labrador's or a collie's, does the job on its own. Some dogs feel the cold a lot more, though.
Dogs that usually benefit
Thin or short coats. Whippets, greyhounds, dachshunds and chihuahuas have little fur and not much body fat to keep them warm.
Small dogs. A small body loses heat faster, and they're closer to wet grass and cold pavements.
Older dogs and puppies. Both find it harder to keep their temperature steady.
Dogs clipped short for winter. If you've had the coat taken right down, they've lost their insulation.
Signs your dog is cold
Shivering, a hunched back, lifting their paws off the ground, or slowing down and wanting to turn for home early. If you see these on a frosty morning, a jumper will probably help.
Why wool
Wool is breathable, so your dog won't overheat once they get moving, and it keeps some of its warmth even when it's damp. That matters on a drizzly walk in November.
A few tips
Take the jumper off indoors so they don't get too warm. Check under the front legs after the first few walks for any rubbing. And dry your dog off properly after a wet walk, jumper or not.
If your dog is older or has a health condition and you're not sure, ask your vet.
Need help with fit? Read how to measure your dog for a jumper, or browse the For the Dog edit.