I live in Denmark os the weather is also a showstopper for me over the winter. But try to ride regularly indoor during the winter, and on Zwift i do alot of races and there are training programs focused on what you want to get better at, races, endurance, sprints etc. So a fantastic platform actually. I ride on a Wahoo Kickr Cor, a mid range priced trainer with fantastic performance, i can absolutely recommend it. Gives a great extra dimension in riding :)