What type of tent do you have?

It depends on several factors. First involves snow load. If you are camping between storm events then your 3 season tent may work fine. Second is wind. If your trips are in areas without high winds your 3 season tent may work fine. I have used 3 season tents for winter camping on numerous occasions, but the conditions were ideal. I have also slept in tarp lean-tos during light snow storms and heavy rains staying comfortable in both conditions.