Is Sept too late for visiting Canadian Rockies?

We absolutely love RVing in the Rockies and Foothills in September after everyone back into work and school routines for the most part. We are often heard saying "if you get bored of the weather, wait 10 mins" = no smoke without fire on that one. Seriously we've been swimming and jet skiing on lakes in mid October in the arctic north, and then at same time other years, skating down the high streets in Calgary. We've even been hit by snow (didn't stick but it did snow flakes) in August driving up 17th Avenue in Calgary also, to say nothing of baseball size hail storms in June/July other years.

Layers are always best, and prepare for many temps. For what we find the best accuracy check Farmer's Almanac