Puppy on Heat

Hi,
It depends on the breed and the individual dog.....  however in the average it is around 9 months but can be as early as 6 months !. 
Best regards,

how abowt a lab

Depending on the breed, usually first heat can occur between 7 and 10 months.  Then usually about every 6 months or so until she is either spayed or pregnant.  Some breeds only come into season once a year.

My vet also told me that 6 months is when my female long hair chihuahua would go into heat and then again in another 6 months.  So it would be twice a year.  If you don'e want any messes, make sure you have diapers to put on the dog and keep it inside so that no males can get to her.