Running - Getting back into shape

I do marathons, but each winter I press my reset button by stopping to run. As soon as temperatures sink below 10°C (plus, that is) I just don't feel motivated enough to expose myself to the elements. Each April I regret my hibernation and resume training, but it's not exactly resuming, it's more like starting from scratch. Now (end of June) I feel like I'm getting back into a reasonable shape (20km runs are possible), but it took me three months to get there. I'll have to think of a different solution for winter...