Do dogs only go into heat in the spring and fall?

No, dogs do not only go into heat in the spring and fall. The heat cycle, or estrous cycle, typically occurs twice a year for most dogs, but the timing can vary based on the individual dog and its breed. Smaller breeds may go into heat more frequently, while larger breeds might have longer intervals between cycles. The heat cycle can occur at any time of the year, not strictly limited to specific seasons.