This is what I found Freedom when I Googled; "Cats Heat Cycles."

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The Breeding Season in Cats

The breeding season in cats is practically year-round, running as early as February, and as late as December, but in the western hemisphere, March through September is generally regarded as the breeding season.

Heat Cycles in Cats

Cats are referred to as "polyestrus," which means that they will go into heat cycles periodically during their fertile years. These heat cycles may start as early as the fourth or fifth month of a kitten's life, and will continue until she is either bred or spayed. Heat cycles in cats last from several days to two weeks or longer, and repeat every two to three weeks. You can see then, how a female cat may almost always seem to be in heat.

Summation

•Heat, oestrus, and estrus all refer to heat cycles in cats.
•The breeding season in cats lasts almost year-round.
•Heat cycles can start as early as four or five months in a female kitten.
•Heat cycles in cats last from several days to two weeks or more
•Heat cycles in cats repeat every two to three weeks until the cat is spayed or becomes pregnant.
•Heat cycles may cause pain or discomfort in cats.

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