Puppies can't regulate body temperature as well as adult dogs. Your puppy can get overheated when exercising on a hot day, so bring along some drinking water. Your puppy can also get cold when out on a winter day.
Don’t exercise your puppy during the hottest times of summer days.
Watch for the signs of heat stroke: excessive panting, noisy breathing, bright red gums and tongue, weakness and collapse.
In winter, watch for signs of cold intolerance, which include: shivering,
stiffness, sluggishness, non-responsiveness, difficulty breathing or lameness/lifting of the feet. These symptoms may be a sign that your puppy has reached his limit and that you should bring him home to warm up.
After you get home from walks, check your puppy's feet for burrs or pebbles. After walking in snow, soak your puppy’s paws in warm water to remove ice and salt from his footpads. Some dogs may benefit from a coat or boots. – Gary Landsberg, DVM, Dipl ACVB and Donna Dyer, CVT