Summer is the most popular time to visit Vancouver. The best festivals and events are organised during the summer months. This is also the perfect time for any kind of outdoor activities and seeing the huge variety of wildlife. The weather is just great, it's warm and pleasant with no rain and cool breezes from the coast. But this is also when you'll have to book your trip in advance. During the summer season, the tourist concentration is the highest.
There might be an increase in tourism numbers between Christmas and New Years, and during the two weeks in March, thus, the prices can go up a bit.