@ Ripple
Yes, your limiting factor won't be temperature as much as hours of sunlight (since we are not talking about hot, long season stuff like corn, tomatoes or peppers, anyway). You will need full sun, which might be a challenge depending on what part of town you are in and which way the land slopes. Also, there is a big difference in how much frost you get at Hastings and Commercial and how much you get at Mount Pleasant Park.
The days have been getting shorter for a month already, and August is when things start slowing down. But things like kale and brussel sprouts don't taste as good until they have taken a good (-5) frost, and I have pulled them out of snowbanks a few times. But I would definitely try gai lan. It should be easy to find there, and it is faster than broccoli. On the upside, you should be planting next year's garden outside in February. As for whether it is worth planting things like carrots now for next year (my worry would be that they would just go to seed) best to talk to a gardener there who knows.