Hi,
I have three toilets in my house. When the weather gets really cold, one toilet looses water. The pumps in the basement go off and drains most of the water. I think it is a vent issue but I don't know where the vents are. Could they be covered with snow or ice? Can I fix in this cold weather or will I have to wait until spring?
I can flush the toilet and water returns but only for a short time. There is also a strong odor when it is low water for a long length of time (like over night).

Have had this problem every winter.

Where do you live?

Do you have a very tight home with a furnace that does not have a fresh air intake?