tgabor

Thanks Patty for suggestions

tgabor

So as I understand it could already snow in Grand Teton in late September ? Is it very probably ?

Patty

It can snow even earlier than late September but the probability isn't high. A storm hit around the middle of September last year. Early snow usually melts/gets cleared quickly.

tgabor

Thanks Patty ! I also have read that in september the fall's colours are amazing, maybe It worth to risk a litke bit to see

Nelson

Once you settle on a route, it's a good idea to become familiar with each state's Department of Transportation website. They will have maps showing current road conditions in near real-time.

In addition to weather issues, they can inform you of construction delays and accidents.

For example, see these links on the Wyoming DOT:
http://www.wyoroad.info/
https://map.wyoroad.info/

Usually weather will be fine that time of year, but as other have noted, you can never be sure.

Patty

I also have read that in september the fall's colours are amazing, maybe It worth to risk a litke bit to see

That's why I'm going this fall!

tgabor

So I can tell to you that we already made our trip between 19 sept - 30 sept
and it was just amazing. The route was Portland - Big Sur ( all the northern part that can be visited ) - Los Angeles - Las Vegas - Zion NP - Nevada Desert - Yosemite NP - Tioga Road - Crater Lake - Portland including a lot of points of interests and attractions alog the trip. We didn't risc the Naciamento Ferguson road ) The weather was ok but not too hot. It was perfect for what we plan to do Due to relatively short time we cannot went to Grand Teton or any other part of Rocky Mountains ... But after all our trip was a great experience, It was very very nice !