How often do female cats (queens) go into heat?

Cats usually start going into heat when they have reached 80% of their adult size. This is usually around 6 months of age, but some queens go into season as early as 4 months of age.

Cats go into heat every 2 to 3 weeks during Spring, Summer and Autumn. The heat itself lasts about 7 days. Cats require light exposure to go into heat – if a cat is kept indoors it can cycle continuously in response to artificial light (Siamese especially).