The best mating season for dogs should primarily consider the following factors:

Breeding Season:
Dogs tend to be more fertile in spring and autumn, specifically between February to April and September to November. During this period, dogs have higher hormone levels, making them more likely to come into heat.

Age:
Although dogs reach sexual maturity between six to eight months of age, it is best to wait until they are fully grown before breeding to ensure their health and breeding quality. Specifically, male dogs are recommended to mate after two years of age, and female dogs after one and a half years. At this time, the dogs' bodies are mature and healthy, satisfying the conditions for mating and breeding.

The optimal breeding age for dogs is between 3 to 5 years old. After 6 years, they enter menopause, and their fertility rate decreases.

Health Status:
Before breeding, dogs should be physically healthy, mentally sound, and have a normal appetite.
It is best to take the dog to a veterinarian for a physical examination and necessary vaccinations to ensure their health.

Mating Time:
The first heat cycle for female dogs typically occurs 8 to 10 months after birth. Healthy female dogs can mate twice a year, but the total mating period is only about 10 days.
The most suitable mating period for female dogs is a few days after the reproductive organs begin to produce light bloody discharge, specifically 10 to 15 days after the start of menstruation. This is when the female dog's reproductive organs will ovulate, making it the best time for mating.

Personality and Breed:
Consider whether the dog's personality is suitable for mating, avoiding aggressive dogs or those prone to conflicts with other dogs.
Different breeds of dogs also have different breeding requirements and considerations, which need to be understood and followed.

In summary, the best mating season for dogs is spring and autumn (February to April, September to November), considering factors such as the dog's age (male dogs after two years, female dogs after one and a half years), health status, mating time, as well as personality and breed.