Sorry to hear about your veggies. Most people here in Ottawa do their planting when Canadian Tire or some other store puts the plants out, but I know our last frost free day is June 10 although we haven't had a late frost in many years. It's June 5 for southwestern Ontario. I found this calculator when I googled which contradicts what I say but they are using new data based on 1981-2010 climate norms.
June 10 seems like a long time to wait, especially when the days are warm, but I guess it's better to be safe than sorry. The loss of my tomatoes was particularly disappointing because I started some new varieties from seed in the coldframe and was looking forward to seeing the results. Oh well, there's always next year!
One of the nice things about gardening is getting another chance next year.