Out of curiosity, are the what is causing the jeans to get wet? Insufficient seal between snow boots and the snow pants, or does the water eventually just get in through the snow pants material?
In deep snow, jeans will get wet and freeze from the knees down. When snowmobiling, the snow swirls around and gets onto the seat of the snowmobile and then melts when you sit on it.
Denim jeans are a remarkably poor choice for wet or snowy activities or emergency winter use. I believe that in really cold conditions if you don't keep your legs warm, there's nothing you can do to keep your feet warm.
Snowpants, or my preference, bibs with full side zippers, will serve as an outer layer. You have the choice of insulated or non-insulated. You can adjust by wearing long-johns, sweats, or cargo pants underneath.
The upside is protection from cold, wind, and moisture. The downside is that snowpants and bibs can make long-distance walking more difficult (especially combined with the ubiquitous pac-boots that even ballerinas wear in Minnesota). Gaiters or nylon outer shell pants would be better for this.