The weather in Canada will vary dramatically across the different areas of the country so when touring in Canada we recommend you pack plenty of light, comfortable clothing that can be easily layered, as well as enough warm outdoor clothing. Rain gear is also a good idea to take as a wise precaution against inclement weather. A comfortable pair of shoes for walking and sightseeing is essential.
British Columbia has the most moderate climate of any region in Canada being bathed by currents of warm, humid air from the Pacific. 
Vancouver and Victoria enjoy pleasant and relatively dry summers and mild, wet winters. Snowfalls are rare in low-altitude regions and when snow does fall it generally melts the same day.
The Rockies have a much more severe climate. The mountains bring a much colder, longer and snowier winter. Summer, however, is just as warm as on the coast. However, weather can change at a moment's notice, so be prepared.
In Ontario, the presence of the great lakes has a moderating effect on the climate, which is not as continental as might be expected. You should still expect summers to be hotter than in the UK, with week-long heat waves not uncommon. The autumn is a favourite for many, with its long, mild and sunny days and bracing nights. In the winter, temperatures average –5°C with very variable weather.
Climate in Atlantic Canada (New Brunswick, Nova Scotia, Prince Edward Island, and Newfoundland & Labrador; collectively also known as the Maritimes) is very variable. There can be heavy snowfalls that melt completely several times per winter. Summers are warm, but not hot, with temperatures around 24°C. Fog is very common, especially from April to June.