The summer months are a good time to see if your attic has been home to squirrels over the cold winter months. As the attic gets hot in the summer, the rodents will leave and take up residence in holes in trees. To see if your attic is home to squirrels, enter the attic without any lights on during the day. If you see light shining through from the outside in small holes, this is likely the entrance they created to get inside. Plug these holes with wire mesh. Just be sure to take this preventative measure in mid or late summer when the squirrels' litters are old enough to vacate the nest to live on their own.