Make sure to keep snowplows away from your tank and drainfield. The plows can compact soil or dig up the area around your system and cause damage.
When the temperatures drop, you may be concerned about your tank freezing. Completely avoid adding anti-freeze or any other chemicals that could harm the balance of bacteria in the tank. If your septic is used regularly throughout winter months, it will in most cases create enough heat to stay thawed. Although if we have a winter with very little snow cover to act as an insulator, it is wise to throw loose hay/straw or insulation around manhole covers and even the drainfield area or mound. Insulated covers are also available to protect against freezing.
If you tend to be away for long amounts of time in the winter, make sure your caretaker is aware of where the septic system is located in case of emergency.