You could end up with weather delays anywhere along the route.
One year I went to Indiana (from Seattle) for Christmas.
Going I took the train - Portland, SLC, Denver, Chicago. We were delayed by snow in the Oregon Blues (i.e. I84), further delayed in Denver due to a late connection from San Francisco (snow in Sierras). But only a dusting of snow on the ground across Iowa and Illinois.
The return train was canceled due to snow in Seattle. Instead I took the bus from Chicago. The direct route via Mpls (I90/94) was cancelled due to a snow storm. I ended up returning via SLC and Pendelton - I80,84,82,90. While it was cold and windy in Wyoming, the only snow on the ground was on I90, Ellensburg to to the pass.