Jul 19, 2025 · Life-saving guide: Spot critical differences between dog heat exhaustion and heat stroke with symptoms chart. How does age affect a dog’s heat cycles? As female dogs age, the frequency and regularity of their heat cycles may change. Learn all you need to know about estrous cycles in dogs with VCA. While there can be extreme variation between individuals in both behavior and physical exam findings in each stage, understanding the A dog's heat cycle is a lifelong process, beginning generally between six and 24 months of age and continuing into old age, with frequency, symptoms, and fertility potential changing over time Site will be available soon. Nov 23, 2024 · Dogs are in heat for an average of 2-4 weeks. Dogs were domesticated from wolves around 15,000 years ago. Both males and females are fertile well into their advanced age. The period that your dog will be in heat can vary but will normally last from approximately 12 to 21 days. The heat cycle of dogs refers to a female dog’s reproductive cycle when she is fertile and capable of mating. Our professional dog heat cycle calculator is a valuable tool for breeders to predict and track the reproductive cycles of female dogs, and helps estimate crucial dates in a dog’s estrous cycle, including the onset of heat, fertile periods, and the end of the cycle.