In Minnesota, plumbing vents can get blocked shut with frost during prolonged sub-zero temperatures. To prevent this, it is recommended to increase the size of the vent before it protrudes through the roof. Increasing the vent size helps to ensure proper ventilation and reduce the chance of frosting. Additionally, keeping the vents short can also help prevent frost closure. There are products available, such as Sewer Skewer, that use copper tubing to absorb heat and prevent frost accumulation. These methods can help minimize the risk of plumbing vents getting blocked with frost in cold weather conditions.