The seasons can affect your dog's behavior, especially when it comes to eating. Hot weather can be difficult for some breeds of dog built for cooler climes. Warm fur and lack of sweat glands mean your dog must struggle through the summer months and this effort may be reflected in his overall attitude and the amount he eats.
All mammals tend to reduce their caloric intake when the weather turns warmer. During the winter months, mammalians must work to maintain a safe body temperature and many calories are burned to do so. In hot weather, mammals tend to do the opposite, moving and working less in order to stay cool enough to survive. According to Doctor Ken Tudor of PetMD, it is the length of the day that notifies the brain how much to eat. For example, on short winter days the brain seeks out food with more intent, while on long summer days the instinct is to cool first and eat second.
Since humans tend to have more going on when the weather is hot, your dog may mirror your actions. For example, at picnics and barbeques there is lots of food and opportunity for your dog to scrounge an extra meal. Although he eats less overall in warm weather, your dog may eat more thanks to the in-between snacks and treats he finds during such events. Your dog may not even be hungry, but the chance to devour a hot dog or some barbequed chicken is too tempting to pass up. Overeating can become a real hazard at these times since human food is higher in fat and calories than most dog foods.
Although your dog's natural instinct may be to eat more during the winter months and less during the summer months, life in your heated and air-conditioned home may have more bearing on the end result. Since pets do not typically have to deal with the hardship of exposure to the elements like wild animals do, your dog may actually eat more in summer than winter. Pets and their masters tend to be more active during the summer months when the weather is hot and the options are plenty. When your dog burns calories, they must be replaced, so an increase in food intake is not unusual despite the heat.
The cold winter months tend to keep your dog indoors. Although you are trying to ensure his safety and comfort, you may actually be contributing to his boredom. Like humans, bored dogs can sometimes end up eating more than they should just to derive some pleasure and pass the time. For this reason you may find that your dog eats far more in the cold weather than the heat. Once the seasons change and you head out more, the boredom lifts and your pup shifts his attention from the next meal to the next toss of the Frisbee.