During the winter, cats' mealtimes will probably be different because it gets darker so much earlier. Cats tend to eat at dusk and dawn. You might have to adjust your feeding schedule. You might also have to provide more food in the wintertime because the cats use more energy trying to keep warm. Monitoring their food bowls will let you know.
If you provide moist (canned) food, also add dry food during the winter because the moist food will freeze shortly after being put out.
Special attention is required to prevent water freezing in winter. You can slow or prevent freezing by providing larger water bowls, by putting water in a place shielded from wind, by placing water bowls in direct sunlight or by using electrically- heated water bowls.
Feral cats need protection from the elements--wind, rain, snow and freezing cold. Your feral colony may already have adequate shelter--ideally a space with at least three sides to block the wind, a roof to block precipitation and a floor to keep paws from getting frostbitten on the frozen ground. Watch the cats as they come and go from the feeding area to see if they have sheltered areas nearby, such as a barn, under a porch or a densely wooded area.
Please provide a warm place for your feral friends, such as a covered porch or a barn for feeding. If no shelter exists, you can build one. This can be as complicated or as simple as you wish. One simple plan uses a large domed garbage can lid and four 12-18" dowel rods. Glue one end of each dowel rod to the underside of the lid, so that they make four poles to hold up the lid. Then either place this in a non-windy area or "plant" the ends of the dowel rods in the ground. The lid will keep rain and snow off the food.
Cat shelters don't need to be expensive or elaborate. Even a cardboard box with a small door cut in it to block the cold wind is better than nothing!
Heating Pads and Heated Water Bowls:
You may also want to invest in an electric heating pad or an electric heated water bowl. These are available online as well as in the majority of stores. If you shop around, especially online, you can find great deals.
Other Dangers: Antifreeze and Ice-melting products are extremely dangerous to cats.
Cats enjoy the sweet taste of antifreeze. But even small doses can be lethal. If you see any leaks under your car (green liquid) please clean it up as quickly as possible. If you think your cat has consumed any antifreeze, please contact your veterinarian right away!
Ice-melting products that are used on driveways and walkways can irritate the cat's skin and mouth (from licking their paws) Signs to watch for: excessive drooling, depression and vomiting. Again, please contact your veterinarian right away!
There is also a wonderful article called "Coming in from the Cold (Helping feral cats survive the winter)" written by Karen Commings, featured in ASPCA Animal Watch.