[Cottonwood]

If you are traveling in the winter most of the Northern Rockies, Idaho, Montana, Wyoming, even western Oregon and Washington, will most likely be buried in snow which limits what you can see and do because you are stuck to the main highways unless you snowshoe, cross country ski or take time to ski at resorts.
If you have time, try driving Highway 95 from North Idaho into Southern Idaho (Boise) is probably one of the most naturally diverse and scenic drives in the West.
Idaho has been touted as one of the most mountainess states in the nation so there is a lot of scenery to take in. The Interstate across southern Idaho misses a lot of the scenic attractions in the South. If you head off of the interstate and take Highway 30 you will be following the route of the Oregon Trail and will see canyons and springs and such which you will not see from the Interstate.
Same for North Idaho--head off of the Interstate and you will see some of the prettiest mountains, lakes, forested scenery anywhere. The largest collection of natural mountain lakes in the West is in North Idaho as is some of the largest stands of forests.
The mountain scenery outside of Boise is gorgeous, but if there is snow you are basically stuck to the main highways.