While cycles can vary, female felines usually go into heat four to five days every three weeks during breeding season starting at about six months of age. (zippivet.com)
A female won't go into heat: Female felines typically go into heat four to five days every three weeks during the breeding season, with some variance in cycles between individuals. (vetcentercity.com)
They are also likely to try and leave the house looking for female felines to help them scratch their itch. (urbananimalveterinary.com)