We visited Jasper/Banff for 8 days in late August and it rained/snowed almost the entire time! It would rank one of my top rides if the weather had been better. I think because of the weather there were relatively few tourists and campsites were no problem to find. Bring lots of $$ as they charge per day for being in the park. I seem to recall $25/day. Add to that a campsite. Also food can only be purchased in Jasper or Banff (there is one restaurant at the glacier).