Frustration with unharmonious latitudes and altitudes is not exactly news. But I was hoping to do better at solving the conundrum than when I was a newbie RVer.
The Columbia River system is to the northwestern USA what the Colorado River is to the southwest. (Notice no upper case S.) Overall the northwest slopes downhill towards Astoria OR, where the mighty Columbia debouches to the sea. (Or shall we be Lincoln-ian and say 'where it rolls unvexed to the sea?')
At the middle latitudes, altitudes are inconveniently high. Credit bad planning by the topo committee of North America. This messes up the autumn migration towards the south. You can't just wait until you are 5 F cooler than you want, and then drive 100 miles south.
It is embarrassing but I really don't have a better and smarter idea about migrating south. Perhaps it doesn't matter so much: as long as Indian summer holds, it is nice at most places. When winter hits, it hits all at once, and you skedaddle quickly without debating the details.
Does it sound defeatist to take this approach to an unsolvable conundrum? Perhaps it is just the opposite. There are many times when you can't just keep pounding away while using the same approach as in the past. Toynbee might say that you transfer the battle to a different level.