When you get frequent nosebleeds in the winter the nosebleeds are usually caused by the dry air that is associated with winter.
During the winter months the air gets dried out and this causes your blood vessels in your nose to crack and then bleed.
This also happens when your furnace is running in the winter which dries out the air in your home.
You can help prevent frequent nosebleeds in the winter months by using a humidifier or vaporizer in your home add moisture to the air which will prevent your nose and blood vessels in your nose from drying out and cracking which will prevent your nose bleeds.