In Indiana we can get as many as 100 freeze thaw cycles in a season.
So, please be very careful when trying to ride the trails in the winter. The best time to ride is when the trail is frozen solid. On days when the temperature goes below freezing at night, the worst thing we can do is wait for the sun to come out and warm up the trail before riding. The trails can be very soft even if it hasn't rained recently. Even if the temperature stays below freezing South facing trails can defrost in sunlight and turn to mush.
If you are leaving ruts in the trail where you have ridden please leave the trail. The ruts will allow even more water to remain on the trail and make it even worse. If people see you riding they will want to ride too, so very soon the trail reaches a point of meltdown.
Here is a nice video from our friends up North at Merrell Trail.