I live in Florida and have a mini schnauzer who does great on long walks (4 to 5 miles) when the weather is cooler. The cooler the better but he does well on long walks up to about 75 F. However, when it gets warmer than 75 F he likes to stick to shorter walks - close to home, stops in the shade and can't wait to get home. In cooler weather he will walk forever and loves it. I think schnauzers tend to overheat easy when the weather is warmer. I wouldn't think of trying a long walk in the summer. In the summer I try to keep him on the grass when it is hot. I also always make sure to have water on our walks. He'll drink it out of my hand so we take periodic water breaks when we go on a long walks.