Cats in heat need special care and attention. If your cat has already been through a heat you won't forget her howling and the constant demands for attention.
If she isn't able to mate then it can be a frustrating and uncomfortable time for you both. If, on the other hand, she is able to mate, you need to be prepared for potentially two litters of kittens a year! Unless you're planning on breeding from your cat it is therefore best to have her spayed. It will be easier on her, and on you.
When your cat is 'in heat' she is in the fertile period of her reproductive cycle and is looking to mate. She will usually go into heat in the spring and Autumn and a heat can last from a few days all the way up to a few weeks. A cat normally has her first heat at around six months of age, but some can have it as early as four months old.
What to look out for
During a heat your cat may be more affectionate, rubbing up against furniture, walls and her favourite people. She'll probably rub with her hindquarters in particular and may frequently display the mating position with her hindquarters and tail raised.
The most problematic characteristics of a heat for an owner are the vocalisation and spraying. Cats in heat will howl loudly and constantly as they try to attract a male to mate. They may also spray walls or furniture with strong smelling urine in an attempt to indicate their availability to a male.
If you have an indoor cat they may try desperately to get outside, even going as far as attacking windows or doors.
Though your veterinarian may be able to prescribe medication to reduce the signs, the best way to prevent a cat being in heat is to have her spayed. After she's been spayed she will stop going into heat and become much less territorial and less likely to spray or scratch.
Most veterinarians prefer to wait until her cycle is finished before spaying. There are arguments for and against spaying a kitten of an early age or waiting until after her first heat. Your veterinarian will be able to tell you what his/her opinion is.