In late August 2014, I drove up to the Canadian Rockies. Day 1 was 550 miles through Washington on I5, connecting to highway 1 and then highway 5 in Canada to Barriere where I stayed in the hotel for a night. It was a very scenic drive. Day 2 was 4 more hours to Mt Robson Provincial Park. With this route I drove to the north end of the collection of Rocky Mountain Parks and then entered to pass down to the south, exiting through Banff National Park.
The first few days were sunny and beautiful with temps in the 70s, but it was downhill from there. I had planned two backpacking trips, but the second one was cancelled due to the weather and I did a lot more car camping than backpacking. I ended up coming home one day early as the rain and cold got tiring to camp in. In Banff NP, the high temps was generally in the low 50s, but most of the time it was in the 40s.