There's a common misconception that termites go dormant as the outside temperature drops. Just because you don't see them does not mean that they are gone. When the temperature drops and the ground is covered in snow, these damaging pest just burrow deeper into the soils. Since they require constant moisture to survive, they will burrow deeper and ultimately find your wooden structures to satisfy their survival needs.
Termites infestation has no specific season. Winter is a good time to treat for termites when you consider the fact that termite behavior is most predictable in the winter months. Termite control requires the initial and recurring expertise of pest control professionals. Termite control does not stop by killing them. You must take active measures to verify that they never return via annual inspections and retreatment when and if necessary.