Exercise routines for older dogs should be adjusted according to weather conditions to ensure their safety and comfort. In hot weather, walk early or late in the day to avoid overheating, and ensure plenty of water is available. Avoid walking on hot pavement, which can burn paws. In cold weather, keep sessions shorter to prevent exposure to cold and provide appropriate clothing for short-haired or small dogs. Be cautious of slippery surfaces, such as ice, which can cause joint injuries. Always monitor your dog for signs of discomfort in extreme conditions.