We went through several different climates on this trip - from freezing in the passes to needing AC in the flatter areas.  There was also extremely limited space in the car, so choice of outerwear was important.  I found myself mostly using my Marmot Tempo.  

It’s made of a super light soft shell material that’s wind and water resistant, but not too warm.  The water resistance was put to the test during a couple of short but enthusiastic rain showers in Yellowstone.  And it held up equally well to a freezing walk at night.  Its light weight and stretchy material made it comfortable to wear in the car, too.  I got this one on sale at REI for half off, so I didn’t expect much from it - I have to say though, I’m impressed, and Marmot will definitely be on my list next time I’m looking for a jacket.  Three issues: The cuffs don’t have thumb holes.  The cuffs are too tight, making it difficult to push the sleeves up.  And a hood would be nice.

All pretty minor stuff though.  Available directly from Marmot for $90.