Yes, it is normal.
Cats are amazingly well evolved creature. They make wonderful pets. They can survive (but not thrive) without the care of humans. Above all, they can reproduce. Few creatures outdo cats when it comes to the matter of reproduction.
Cats are induced ovulators. This means that female cats in heat don’t release eggs unless they mate. If an in-heat female cat does not mate, she does not release any eggs. After the heat cycle is over her body goes into express mode and the female rapidly goes into heat again, and again, and again, and again until she gets pregnant, is spayed, or, rarely, mates without getting pregnant. In the last case the cat will enter a state called pseudopregnancy–her body will think it’s pregnant and she won’t go into heat again . . . for a couple of months.
These rapid heat cycles increase the total number of kittens that a cat can have in her life.
If you don’t spay your cat you should expect her heat cycles to come rapid-fire until she gets pregnant. If you’re not interested in finding homes for kittens then you should spay her immediately.
Photo: they’re cute, but do they all have homes?