How long will my dog stay in heat for?

If my dog goes into heat on sept 22, and she fails to get pregnant, is she supposed go into heat again in december?

Hi,

Ordinarily, the stage lasts for 4 to 13 days. Your female will stand still and hold her tail to the side when you touch her back or a male dog tries to mount.

You should consider your pet to be 'in season' for 21 days: 7 days coming into heat, 7 days in heat, 7 days going out. Though conception is most likely during the middle 7 days, Mother Nature doesn't always follow the rules. Confine your pet for the entire 3 weeks.