The campgrounds in the parks are open through September. There can be snow any time of year. We had snow in Banff in August, 2006.
The roads between Banff and Jasper are well-maintained. There are a few significant climbs.
There is never enough time to do and see every thing. Below is an outline of our last visit. We were traveling with a couple making their first trip; they wanted to do all they could in nine days. Sarah and I usually spend 5 in Banff and 8 or 9 days in Jasper
Banff:
Day 1: Tour Banff, Bow Falls, Gondola ride to top of Sulphur Mountain, Upper Hot Sprinds.
Day 2: Lake Louise, Morraine Lake (many get to Lake Louise and make the mistake of not seeing Morraine Lake), Drove part of Icefields Parkway (Crow Foot and Bow glaciers) Herbert Lake
Day 3: Lake Minnewanka, Johnson Canyon was too crowded so we did the Silverton Falls trail. Drove into Kootenay National Park and did the Marble Canyon trail
Drove to Jasper
Jasper:
Day 1: Patricia and Pyramid Lakes, tour jasper, did laundry.
Day 2: Hiked part of Maligne Canyon Trail (bridges 2, 3 and back to 1) Viewed Medicine Lake then continued on to Maligne Lake.
Day 3: Drove back down the Icefield Parkway to the Ice Field Center. (Don't miss the short movie - by far the best I've seen at a visitor's center.) Hiked to the toe of Athabasca Glacier. Seeing the markers of where the glacier used to extend gets one attention. Stopped at Sumwapta and Athabasca Falls on the way back to Jasper.
Day 4: Drive to Mount Edith Cavell. Always interesting to see how Ghost Glacier has changed. One has to look closely to see changes in Angel Glacier.
Drove to Radium Springs in Kootenay National Park.
Note: We traveled with 4 dogs, our friends with 3. In Jasper, we took the dogs swimming in Pyramid Lake every day. We took some or all of the dogs with us on some of the day trips.
Have fun, do what you can and start planning your next visit.
Tom
2015 Meridian 36M
2006 CR-V toad
3 golden retrievers (Breeze, Jinks, Razz)
1 border collie (Boogie)