Canada is a very large country with a lot of geographical diversity, meaning that the climate varies depending on when and where you go.
Winters in Canada, between November and March, can be very snowy and in places like Manitoba and inland of British Columbia, winters are freezing with average lows of -50m which is when the world famous ski season gets underway (from late November until mid-May).
Summer on the other hand, can reach a balmy 25 with relatively little rain, providing a very pleasant and mild holiday.