They can have two litters a year, one in the spring and one in the late summer. Babies can be blown out of nests in higher winds. Most people know where the squirrel nests are.
If you know where the squirrels nest are in your yard. You can reunite the babies with their mother by nailing a box about five feet up on the nest tree or on a nearby tree.
This is a comfortable height for you to reach, and the babies are off the ground and safe from predators. Then place the babies in the box using the rice sock described above. You may need to reheat the sock as Mom may be out eating and may not know right away that the babies have fallen from the nest. If you do this in the morning and they are still there in the late afternoon, call a wildlife rehabilitator that takes in squirrels or small mammals.