Possibility of flying into Jackson. Any idea what kind of weather we would be encountering? Oct 20-28. I believe the temp would be in the 50s, but not sure if it could possibly snow.

Certainly possible. Don't try driving a rental car with summer tires and then waking up in the morning to 3+ inches of snow.
Why not fly to SLC and save some money?
If there is snow in GTNP and Yellowstone, you can go south to Arches and the southern Utah National Parks.
I consider landings at SLC to be safer in poor weather than at Jackson.

Services in Yellowstone shut down around mid-October, and they let snow accumulate on the roads (to groom it later for snowcoaches during the winter season), so you could be prevented from entering the park at all if there's a good snow.

Yellowstone will be closed. We were there for the last weekend of the summer season (Oct 15th week) and it snowed on the last day. A big, stay on the ground kind of snow).

We were in Jackson two years ago in June and the forecast on the board at the Visitor Center at Moose was for possible snow. We wore fleece sweatshirts for a lot of that summer trip.

I've flown into Jackson in the winter. I disagree with the earlier advice. I'd rather fly into Jackson than drive from SLC in winter, but that's just a personal preference.

Snow is definitely possible.

I went to the Grant Tetons in the second week of October 3 years ago. It was warm and mild when I arrived. On the third through fifth days it snowed during most of the day and usually stopped by sunset. And there was frost on my windshield each morning.

I had no trouble driving in the snow in GTNP - the roads were quickly cleared - but had to turn back on two separate attempts to Yellowstone. On the second attempt I managed to get about 10 miles in Yellowstone but met some people who told me they were closing the roads to OF further north, so I just turned back.

The snow was beautiful and didn't spoil my trip in the slightest, but it was unexpected. Now I know it's definitely possible.

On my last day it was warm and sunny again and the snow was completely melted.

panecott, Yes, that sounds like typical fall Rocky Mountain weather! Usually very beautiful then.

I thought Yellowstone was open all year.

Here are the closing dates for Yellowstone entrances and roads:
http://www.nps.gov/yell/planyourvisit/hours.htm

Lee Ann

Yellowstone is open all year, but not all of the roads allow wheeled vehicles.

I was there in February and the only place you could drive your own car was around Mammoth. Between Mammoth and OF, you had to take a snowcoach, which is a bus on tank-like tracks. I don't know what it was like south of OF.

I don't know exactly when they close certain roads, if it's a specific date or if it depends on the weather, but I tend to think it's the latter.

Nelson, yes, I felt like I experienced three seasons all in the space of a week!

Out of curiosity I just looked at half-dozen SNOTEL sensors in the region and randomly picked some monthly October data from various years. There was always some snow by late October. In some cases the snow had come earlier and then melted by the end of the month, but often it came towards the end of the month and that was the beginning of the winter snow pack.

http://www.wcc.nrcs.usda.gov/snotel/...g/wyoming.html

Have a great trip, it's wonderful up there.

One factor is that you will be at altitude, so snow and cold will come earlier. By that time in October, chances are it's snowing fairly often, although it might not be sticking around in ernest. Temp wise, you could see nighttime drop well below freezing. The leaves probably will be completely changed and dropped before your arrival. No crowds to contend with at that time.

Although most roads should still be open, weather permitting, most facilities in Yellowstone will be closed (some will reopen for the winter season on December 15).

From the NPS Yellowstone website:

"2012 Fall Road Closures:

•October 9-Roads close to the public at Tower Fall to Canyon Jct. and Long Lake via Beartooth Pass to the Montana Stateline. (GATES CLOSE AT 8 A.M.).

•November 4-all park roads closed to the public at 8 a.m. except from the North Entrance to Upper Mammoth Terrace, and Mammoth via Tower Junction to Northeast Entrance. Cooke City via Colter Pass to the Long Lake gate is not maintained for wheeled vehicle travel.

Fall weather is unpredictable; roads may be closed temporarily by snow or other weather conditions. Snow tires or chains may be required. Please Note: The section of the Beartooth Highway (Highway 212), between the junction of Highway 296 and Red Lodge, Montana, closes in winter on a schedule determined by amount of snowfall. Travel between Red Lodge and the Northeast Entrance is not possible on Highway 212 until it opens again in the spring."

Thanks to all for the information.

Now thinking of not going. We don't have air tickets yet, so we don't have to go. Perhaps another time. Just thought we might miss the hoards of people during the summer season. Maybe next year in early September

Just move it up a few weeks. We were there the last weekend of the summer season - and it was fabulous. No crowds. Very relaxed. We stayed in a room overlooking Old Faithful. Just a great time to go. The weather can be cold anytime from June to October. Pack layers and you'll be okay.

Agree with starrs. We have been there in early October and it was spectacular. September is also wonderful. Just move it up a bit.

On our October visit, it did snow, but not until at the end of the week. We did get caught in a pretty heavy snowstorm driving from Jackson to Salt Lake City, though.

September is my favorite time to go!!

We were there Labor Day weekend in 2006 and it snowed on us in JH the one day and YNP the next day. Not heavy enough to close roads but certainly cold enough that we were buying up extra fleeces at the souvenir shops in Gardiner.

If you haven't been, then I don't think October would be a good experience. The winter options aren't available there at that time and the summer options really aren't either.

For almost all the National Parks-Most of them have better times to go than others. That said, the off season can certainly be unique and uncrowded.

"...and the summer options really aren't either."

I disagree. I did not find that to be true.

What is missing in October (before the summer season closing date)?

Some in-park facilities close in September, so you could not stay at Canyon or Roosevelt in October, for example. Not a reason to avoid going in October, but a factor to consider in planning lodging and driving.