Though you might want to shy away from Saskatoon in the winter, there is no better city in the summer. There are many activities going on, from the Fringe Festival in early August to the Exhibition in mid-August. Perhaps the best thing to do in Saskatoon in the summer, however, is the three-day Folkfest in August, where pavilions of cultures from around the world are set up in local venues. One can sample food and drink, watch shows, and buy crafts from other countries. It is a tremendously fun time to be in the city.
During this time, the riverbank is also lovely and lends itself well to walking and cycling. Check out the Bessborough Gardens for any bands that might be playing. Make sure to see Wanuskewin Heritage Park for local aboriginal culture. Tennis courts are free, and get some people together for free beach volleyball at the Sutherland Hotel. For cheap (though not exceptional) Indian food, try Taste of India on 8th Street at Broadway. For expensive and delicious Indian food, Taj Mahal is just around the corner on Broadway.
Quick Tips:
Great bike repair and service at Bike Universe on Broadway.
Best Way To Get Around:
An okay (but not great) bus system exists. Sundays and late nights are very difficult. The city is small enough that a bike gets you almost anywhere, and if you stay in the downtown/Broadway area you can get many places on foot.