Late September Western US Backpack Trip

http://lar.wsu.edu/airpact/gmap/ap5/ap5smoke.html

I do trips in late September in north Oregon/south washington cascades.  Snow unusual but it can rain a lot and make trip unpleasant. Look at weather reports.

Mt Hood seems to be better smoke wise.  Maybe Mt Adams or Goat Rocks.

Glacier Peak or Mt Baker look pretty good but I’m not so familiar with them

I just noticed the Swift Creek are in Trinity Alps has a large fire.  Nice area.  I hope it survives.

Glacier Peak area in Wa. is gorgeous and thrilling. However, there’s lots of smoke in parts of Wa. too. Pasayten is nice too. There’s a loop in Glacier out of Holden on lake Chelan that might fit your 6 day time frame. Or you can approach other routes on a road just north of Wenatchee, on the route to Lake Chelan.

I wouldn’t bet on Pasayten or Entiat area. There’s still time for those very-fire prone areas to burn this year and multiple fires have been burning around the edges as well as up in BC to the north. At the very least, I think smoke would be a real possibility…

I have not done the Pecos in September but I used to do it early in the Spring. Given that it’s so far south its probably about as safe as anything in September. Should be a nice time, aspens should be out, the tundra will have some color. If it did snow you could bail to a lower elevation area.

Have you considered Yellowstone? It should be fine in September and less crowded (I assume)

I was in the Pasayten in late September in 2018 and it was a great trip, the larch were turning color and were magnificent and the weather was great during the 5 days I was there, aside from the first night with cold rain that turned to snow overnight.

I’d also suggest hiking along the Middle Fork of the Salmon River in the Frank Church-River of No Return Wilderness in late September — great hot springs to soak in and cool scenery, and not very crowded since the river is too low by then for most rafting along its length.

The Gila?

The Gila?

The Gila is usually easily doable in September (though watch for late monsoon storms), but the OP wanted mountains, so thinking more alpine (I’d say the Gila is more arid/canyon)..

The Pecos in more northern NM (east of Santa Fe) is pretty nice.