Summer in Victoria, B.C. is mild but bring along an umbrela.
Banff/Lake Louise/Jasper, Alberta are usually dry and warm during the day but can be windy and chilly; at night the temperature can dip quickly. We used to joke that there are only two seasons there - summer and winter and possible to experience both on the same day if unlucky.
suggested list to bring:
- umbrella
- summer clothes and jackets
- windcheaters
- flease cardigans
- something nice for that special eveings or "tea" at Fairmont Empress Hotel in Victoria
Hope the above helps and have a nice holiday.