Anytime the weather is warm. Cats are designed to give birth only during warm months (spring through early fall)when the days are appropriately long. Estrous cycles will occur at intervals ranging from four to 30 days but are typically 14 to 21 days apart. Cats as young as three months can become pregnant. A few cats will have an estrus period, in which they may become pregnant if bred, at about 7 to 10 days after kittens are born. Most cats will actually have suppression of estrus during the period they are producing milk for the kittens and then come into heat a couple of weeks after the kittens are weaned.
These silly cats where I live have kittens year around. I once had a litter under my deck at Christmas. I did bring them into the warm garage. There for sure are 3 to 4 litters per year. If you want a kitten I'm sure it will be super easy to find one. Check petfinder for the shelters in your area. When you get your new baby please post a picture! Good luck!