How do I find a snow Monte Carlo track?

Unfortunately, they set every time trial up in the most basic and boring way possible. All locations use the same Summer season and times of day, and also zero degradation for incredibly flat and smooth unrealistic dirt and gravel stages. Summer in Monte Carlo = no snow and ice on the roads.

If you want to run Monte Carlo with snow and icy road conditions at the higher elevations, you have to do a custom Winter Monte event in quick play, or do one of the other modes where it's forced Winter. Should be Winter in Career/Championship modes for example, but quick play gives you more choices for cars and control over everything else like weather and time of day, too.

Codemasters should really consider allowing more options for each TT stage in a future update. They could use the same leaderboards with a couple more columns, and flag the various runs for things like season used, level degradation used, and add filters so you only see what you just ran by default on the boards, but allow you to custom filter and view whatever you want. They seem to be very strongly against adding new leaderboards (even just for Winter Monte) since there's already so many in the game, but they could be using existing ones better by tracking and displaying a few more bytes of data and using filters, while also giving players a lot more flexibility and replayability and new types of competition in time trials.