US mountain west in May

Snowman9000 wrote:
In the time frame May 1 to June 15, what areas, national parks, etc., would be difficult or impossible due to snow and cold?

I know it's a broad, vague question. We plan to be out to AZ in early May for a family thing, and want to take our Class C and work on our bucket list. And that list is just an general idea in my mind:

-Grand Canyon
-Colorado, Utah
-Yellowstone
-etc (see the big NPs and mountains out west)

I would not count out Yosemite too. As I say, it's a very vague idea.

So I'm just looking for some general guidance on when areas open up and are reasonably beyond winter.

In most of Colorado, at least the parts that are NOT the eastern plains, you'll likely encounter snow at a goodly number of locations and elevations that early in the season. Most CG/RV Parks don't open until mid- to late-May. I've already started looking at the reservation calendar, and for the locations that I want to reserve, most of them don't open until the weekend of May 19th or thereabouts. Keep in mind that in Colorado, March and April are among our snowiest months, late season snows are not uncommon. Planning to arrive in Colorado later in your itinerary will give you more options, and if you can extend your time in Colorado to later in June, so much the better.