Banff / Jasper in mid-late Sept. - early Oct.
 

Trying to plan a quick trip and this is the only time available. Is this a good time to go? I note that the "historic temps" range from 40s to 50s F, which I think could be good temps for hiking. I'm just curious if there would be snow that early.

Will only have ~7 full days - how much time would you recommend in each place? I'm thinking 3 days in Jasper and 4 in Banff.

Thanks for your help.

It's the mountains, so absolutely there could be snow, and not just at the higher elevations. On the other hand, it could be absolutely glorious sunshine and little-to-no snow... it's the mountains. =)
Given that Lake Louise is closer to Banff, I think 4 days in the Banff area is great, you may want to include one of your Jasper days as a travel day toward Banff National Park. There might be some nice accommodation options at Castle Junction that provide access to Banff and LL, as well as toward Kootenay National Park should you feel so inclined. It won't be for lack of fantastic scenery to experience, for sure-- that is everywhere! Prepare to be in awe...

Thanks. I've req'd res'v at both LL and Jasper, but have yet to hear back. Have flight tickets on hold. IF all works out, this will be the fastest I've planned a trip - all in one day!

Those "historic" temps are for the townsite areas, which are at lower elevations. It's colder as you go higher. Subalpine elevations (above 4500 - 5000 feet) can start accumulating snow by mid-September some years, other times it's two or three weeks later. Getting into October is getting late for hiking, although there have been years when the higher trails are still fine then. Mid-to-late September can be a great time for hiking if the weather is good - there is often a period of sunny days and cool nights at that time of year.

We have visited during the first couple weeks in September--one trip we had a lot of rain and the other trip we had near perfect weather. We had snow on the trees and trail one morning at Peyto Lake--it had rained in town the night before.

You can often find discounted accommodations that time of year. I had made reservations with no cancellation fee and did change them when I found better rates--I do a quick check on www.kayak.com.

We like to stay in Lake Louise because it is closer to the hikes we like to do. Last visit with 7nts, we spent 1 at the airport (late arrival), 3nts at Paradise Lodge on their hikers' special, 2 nts in Jasper at Patricia Lake, and 1 nt Banff at the Rimrock. We have also stayed at Baker Creek, Emerald Lake Lodge, and Beckers--all were very nice. Our last visit was in 2008--I have a trip report posted here. We would love to return.