When Do Dogs Go into Heat?

Female dogs generally start heat at 6–8 months; males start a bit later, usually 7 months to about 1 year. Females heat on average twice a year—once in spring (Mar–May) and once in autumn (Sep–Nov), about six months apart. Males have no fixed heat period and are triggered by females in heat.

A female in heat becomes restless, cries at night, has swollen genitals, pink and clear mucus from the vulva, and loses appetite. A male in heat urine-marks everywhere and may fight other males over mating rights. If you don’t plan to breed, neuter the dog after heat ends.