We are planning a trip to Zion and Bryce, with a fun stay in Las Vegas to see Elton John at the end of the trip...what is the best time to visit these national parks, spring or fall, and which weeks would you pick?

I've love them both. So don't think you can go wrong.
In the spring the trees are leafing out and it is so gorgeous and such a welcome relief from Winter. However the last few years winter has seemed to last into May, so spring has come late. Zion in the fall is also wonderful with the cottonwood turning yellow and the cooler temps from the summer. You'll have a better chance of good weather in the Fall I think. If you are planning to hike the Narrows you will also have a better chance that it will be open. (didn't open till mid to late June this year)

Bryce in April can still have snow, but May can be wonderful (or as this year still getting snow). Weather is such a hard thing to predict.

Fall. The Narrows might not be able to hike in the spring, due to rain or high water volume. IMOP, you don't want to miss The Narrows. Considered by many as one of the Top 5 dayhikes in America. Angels Landing is also Considered a Top 5 by a lot of folks. Both are spectacular. Even if you don't hike either one, there is still plenty of other great hikes there. Fall tends to be busy and crowded though.

I was in Bryce the middle of May and it was cold and snow flurries.

I've also been to both Bryce and Zion the very start of June and the middle of September and the weather was warm and beautiful both times in both places.

I think late September is probably going to be our choice, based on all this feedback. Thank you very much!!

My husband and I went around the 24th of Sept of 09' and it was absolutely perfect. the narrows was warm enough and the most amazing hike we have ever experienced. I agree 100% with spirobulldog! Nothing was crowded. It was definitely cooler in Bryce; the wind was ridiculous the day we got there. I have been to Italy, Mexico, England, France, Spain, Sicily, and Croatia but nothing seems to compare to the memories I have of Bryce and Zion. You will love it! P.S...check out a place call Willis Creek while visiting Bryce. It is a hidden gem not many people know about...was a surprise highlight of our day.

I like both the spring and fall. But as spirolbulldog has mentioned, if you want to hike the narrows, then you will probably want to go in the late Sept. The last couple of times we've been in the spring the river was to high and fast and the narrows hike was not allowed.

Utahtea

There is a certain point in the fall where you can drive yourself around Zion. It's also easier to get a room inside the park then, as well. To eat breakfast in the Lodge, as the sun starts to illuminate the walls of the canyon, is spectacular.... We were there in early December: YMMV.

I believe the shuttles stop at the beginning of November except on Weekends. Then after Thanksgiving there are no more shuttles.

We love the shuttles and it makes hiking and parking very easy especially if you are camping. We like to do the Emerald Pools starting at the Lodge and end at the Grotto. With the shuttle buses you don't have to worry about where you parked...you just pick up the shuttle bus.

We've been in late Nov. - early Dec. and it can get pretty cold....burrrr.

Utahtea

The weekend shuttles in November are optional, but they are a better deal than driving up the canyon since there is still enough traffic to make finding a place to park by the trailheads and viewpoints difficult.
I went with some friends this summer who were very hesitant and a bit negative about the shuttle wondering why they couldn't take their car. It didn't take more than half an hour for them to be sold. It is the best idea for that canyon.

We've not yet been in the Fall, but April has always been a lovely month for us in Zion. It's been warm in the day and cold at night - with perfect temps for hiking. It is true that you would not likely be able to hike the Narrows, but there are so many great hikes and Zion is such a beautiful place, there is much to experience there. We've done the Narrows in the summer when it was miserably hot outside, making the cool water temp inviting. In April we have had on and off rain, which did not ruin a thing.

Depends on who you're traveling with. If you have kids and are at the mercy of their school schedules, then you'll probably be limited to spring break or summer. The parks start to get busy around the spring break holiday, but that can mean different times to different school districts. In Page Arizona (where we lived for 15+ years), spring break typically implies mid-March, but in Wyoming, where we now live, it tends to coincide more with Easter (which will occur on April 8th this year).

If you'd prefer to avoid the rugrats, I'd definitely choose autumn, meaning late September to mid-October. The foliage changing colors is absolutely spectacular. The process typically begins in mid-to-late September at Grand Canyon North Rim and Bryce Canyon since they are both 8,000' above sea level, but will be later for those parks at lower elevations such as Zion.

Here's a video that discusses the four seasons and their pros/cons ->: http://youtu.be/Jq7hayjEcs8

We went to LV< Bryce and Zion in the beginning of April for Easter vacation about 10 years ago and woke up to 8 inches of snow. It was beautiful and there were no problems geting around.

Mid October in Utah is UEA (Utah Education Association) fall convention. The kids are out for two days. This year it was the weather was still good and the parks were full, everyone trying to get in one last trip.

Meaning, crowds are hard to avoid. They have never made it an unpleasant experience for me yet.

We were in Zion in Mid October during the UEA long weekend where Utah schools were out. We avoided the shuttles and just relaxed those days. The shuttle buses we saw were packed like sardines! By Monday, there was hardly anyone in the park and we ventured down the canyon on the shuttle.

Utahtea