How long does a cat stay in heat?

Up to a week at a time (sometimes more) and they can cycle every 3 weeks. Hope you get her in soon to be spayed. In the meantime keep her inside and away from doors/windows and get ear plugs.

This is why its recommended to get them done by 3-4 months old.

Consider yourself lucky that she has not gone through many cycles of being in heat, as she could be sexually mature at 4 months of age. Typically, a heat cycle lasts 5-7 days, and you have a several week window before she goes into heat again. So often, making the appointment 10 days after she starts is what you want to do. But vets will often spay a cat is she is in heat, with a slight additional charge.

Cats do not cycle the same way humans do. When representing the feline cycle, we draw it in a wave unlike the human cycle which is drawn in a circle. Once a feline goes into "heat" she will continue like that until she is bred. There are "highs and lows" hormonally, but until copulation occurs, they will continue in that cycle. The reason for this is that felines do not ovulate until copulation occurs. Penetration creates a chemical reaction which causes ovulation to occcur, thus stopping the heat cycle. Human ovulate once a month (usually) regardless of what events occur during that time period. So to answer your question, she will stay in heat until she is spayed, but she will have short periods of time when it is not so obvious because her hormone levels are on the low end of the wave. I breed cats for a living and I have had girls that are vocal for weeks and others that are only vocal for a few days at a time, then they appear "normal" for a few days, but will again appear to "go back into heat". So it really depends on your cat's purrsonality as to how long she displays this behavior.

I looked this up recently, and there seems to be a lot of variation. Some cats are in heat for only a day or two at a time, but others are in heat almost all the time except when they're pregnant.

When your cat is spayed, though, she will stop coming into heat, of course.

It's called 'on call', not 'in heat'. The queen stays on call for 5-7 days, although up to 20 is possible.

usually 3-5 days.